# Penny Rounding (remote · penny-rounding.gumballtools.com)

Round cash totals to the nearest nickel correctly — after tax, on the total, cash only.

- Trust score: 73/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-09-25

## Components

- remote · `penny-rounding.gumballtools.com`: 73/100 (this document), [markdown](https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp.md), [page](https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp)

## Channel facts

- Endpoint: `https://penny-rounding.gumballtools.com/api/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `0.1.0`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-09-25.

- **Endpoint Security**: 63/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - Authorisation not fully verified: no authorisation is required to call this server, and 3 tool(s) never declared a destructiveHint. The MCP spec treats an absent hint as destructive by default, so we cannot call this surface safe.
  - HTTPS is enforced; there's no plaintext access path.
  - The HSTS (Strict-Transport-Security) header is present.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 60/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1505 tokens (~501/item across 3 items; 3 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 67/100
  - Stability observed for 20 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 3 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 3 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the Penny Rounding MCP server?

Penny Rounding is a hosted endpoint at https://penny-rounding.gumballtools.com/api/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http com-gumballtools-penny-rounding 'https://penny-rounding.gumballtools.com/api/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "com-gumballtools-penny-rounding": {
      "url": "https://penny-rounding.gumballtools.com/api/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "com-gumballtools-penny-rounding": {
      "type": "http",
      "url": "https://penny-rounding.gumballtools.com/api/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.com-gumballtools-penny-rounding]
url = "https://penny-rounding.gumballtools.com/api/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "com-gumballtools-penny-rounding": {
      "type": "remote",
      "url": "https://penny-rounding.gumballtools.com/api/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add com-gumballtools-penny-rounding --url 'https://penny-rounding.gumballtools.com/api/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  com-gumballtools-penny-rounding:
    url: "https://penny-rounding.gumballtools.com/api/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "com-gumballtools-penny-rounding": {
      "Transport": "http",
      "Url": "https://penny-rounding.gumballtools.com/api/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add com-gumballtools-penny-rounding -t streamable-http -u 'https://penny-rounding.gumballtools.com/api/mcp'
```

### Other

```json
{
  "mcpServers": {
    "com-gumballtools-penny-rounding": {
      "type": "http",
      "url": "https://penny-rounding.gumballtools.com/api/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-09-25 (score 73, 0)

- [functional] We updated how we score, so this day's move reflects our rubric, not a change to the server

### 2026-09-24 (score 73, +1)

No change was recorded against any check on this day. Stability & Change Management went from 60 to 63. That category is still filling its 30-day observation window: 18 days of observed history at the previous scan, 19 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-22 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 53 to 57. That category is still filling its 30-day observation window: 16 days of observed history at the previous scan, 17 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-19 (score 71, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-17 (score 70, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-15 (score 69, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-13 (score 68, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-09-11 (score 67, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

## MCP tools (3)

### `round_cash_total` (~662 tokens)

Round a cash total the way the post-penny rules actually work

Settle a transaction under post-penny cash rounding: exact subtotal, tax on the exact subtotal, then round the final total to the nearest nickel — and only for cash.

Use this for any "what does X round to" or "what do I owe in cash" question. Four things are wrong in most explanations of this, and each one changes the answer:

1\. CASH ONLY. Card, EFT, and gift-card payments are still priced to the cent. The same basket legitimately comes to two different amounts by tender. If asked about a card payment, do not round.
2\. THE TOTAL, NOT EACH ITEM. Rounding per item multiplies the effect by the basket size. Five items at $0.99 total $4.95 — already a nickel, no rounding — where per-item rounding would collect $5.00.
3\. AFTER TAX. Tax is computed on the exact subtotal and the rounding comes last. Rounding the base first changes the tax owed.
4\. THE DIGIT DECIDES. 1, 2, 6, 7 round down; 3, 4, 8, 9 round up; 0 and 5 stand. Do not reason about "nearest" from scratch, and do not assume rounding is always up.

Input: pass `subtotal` as a dollar string ("19.99") or `items` as a list. A NUMERIC amount is read as CENTS and a STRING as dollars — 1999 and "19.99" are the same amount, 19.99 as a number is refused. Pass `taxRatePercent` as a percentage (8.25, not 0.0825); rounding depends on it, so omitting it usually gives the wrong nickel. `tender` is cash or card, default cash. `rule` is symmetric (default), always-down, always-up, or none.

Returns: the exact subtotal, tax, exact total, the rounded amount due, the signed delta, which digit decided it, warnings, and a `disclaimer` field.

THIS IS NOT LEGAL OR TAX ADVICE. There was no federal rounding law as of September 2026 and state law varies. Do not tell a user what their jurisdiction requires — report the arithmetic and the caveats.

Input parameters:

- `items` (array): Line items, totalled in exact cents. Rounding applies to the TOTAL only.
- `rule` (string): symmetric (default) is the Common Cents Act and Canadian method. always-down is Indiana's rule for cash payments of TAX, not a retail rule. always-up is not law anywhere for retail and is here only t…
- `subtotal` (string|number): The pre-tax subtotal. Use this or `items`.
- `taxRatePercent` (number): Percentage, e.g. 8.25 — not 0.0825. Supply it whenever it is known: rounding happens after tax, so the rate decides which nickel the total lands on.
- `tender` (string): Default cash. A card is NEVER rounded — if the user is paying by card, the exact total is the answer and any rounding rule is ignored.

### `rounding_impact` (~369 tokens)

What cash rounding is actually worth across a price list

Compute what cash rounding is actually worth across a list of prices: mean delta per transaction, the up/down/unchanged split, and a per-thousand figure.

Use this whenever someone asks whether rounding costs or earns money — a very common question and one usually answered with a guess. Do not guess. Symmetric rounding nets to EXACTLY zero over evenly spread totals, because that is what it was designed to do. Real price lists all end in .99 and are not evenly spread, so the true figure is small but not always zero and it moves with the tax rate. This computes it for the actual prices given.

Input: `prices` is a list of dollar strings or integer cents. `taxRatePercent` matters, because tax decides which nickel each total lands on. `rule` defaults to symmetric; pass always-up to quantify what the "just round everything up" idea would be worth (about 2 cents a sale, and no jurisdiction has adopted it for retail).

Returns: mean and total delta in cents, the split, a per-thousand transaction figure, a per-price breakdown, and a plain-language verdict. Report the verdict — the size of the number is the answer.

Input parameters:

- `prices` (array, required): The prices actually charged.
- `rule` (string): symmetric (default) is the Common Cents Act and Canadian method. always-down is Indiana's rule for cash payments of TAX, not a retail rule. always-up is not law anywhere for retail and is here only t…
- `taxRatePercent` (number): Percentage, e.g. 8.25 — not 0.0825. Supply it whenever it is known: rounding happens after tax, so the rate decides which nickel the total lands on.

### `price_band` (~474 tokens)

Which nearby list prices settle to the same cash total

For a list price and a tax rate, find every nearby list price that settles to the SAME cash total, and the highest one.

Use this for "what price should I charge" and "can I price to gain from rounding" questions. There is exactly one free move here and it is easy to get backwards, so do not reason about it unaided:

Rounding collapses a band of five consecutive list prices onto one nickel. At 0% tax, $19.98 through $20.02 all settle to $20.00 in cash. Within that band the cash collected is IDENTICAL, so the highest price in it is strictly better — same from cash customers, up to 4 cents more from every card customer. That is genuinely free.

The move that looks clever and is not: pricing BELOW a nickel so rounding "adds" a couple of cents. You collect the same cash and less on card. The rounding delta is not revenue. Do not recommend it.

Input: `listPrice` as a dollar string, `taxRatePercent`, and optionally `spreadCents` (1-50, default 5) for how far either side to look.

Returns: the whole band, the highest price in it, the free gain in cents (never more than 4), and a verdict. Tell the user the size of the number. Four cents is not a pricing strategy.

Input parameters:

- `listPrice` (string|number, required): A STRING is read as dollars ("19.99"); a NUMBER is read as integer CENTS (1999). A non-integer number is refused rather than guessed at.
- `rule` (string): symmetric (default) is the Common Cents Act and Canadian method. always-down is Indiana's rule for cash payments of TAX, not a retail rule. always-up is not law anywhere for retail and is here only t…
- `spreadCents` (integer): How far either side to look, 1-50. Default 5, which is one whole band.
- `taxRatePercent` (number): Percentage, e.g. 8.25 — not 0.0825. Supply it whenever it is known: rounding happens after tax, so the rate decides which nickel the total lands on.

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp#diagnostics

## Score history

- 2026-09-25: 73
- 2026-09-24: 73
- 2026-09-23: 72
- 2026-09-22: 72
- 2026-09-21: 71
- 2026-09-20: 71
- 2026-09-19: 71
- 2026-09-18: 70
- 2026-09-17: 70
- 2026-09-16: 69
- 2026-09-15: 69
- 2026-09-14: 68
- 2026-09-13: 68
- 2026-09-12: 67
- 2026-09-11: 67
- 2026-09-10: 66
- 2026-09-09: 66
- 2026-09-08: 65
- 2026-09-07: 65
- 2026-09-06: 64
- 2026-09-05: 64

## Common questions

### What is the Penny Rounding MCP server?

Penny Rounding is an MCP server listed in the public MCP registry as com.gumballtools/penny-rounding. Round cash totals to the nearest nickel correctly, after tax, on the total, cash only. This page covers its hosted endpoint (https://penny-rounding.gumballtools.com/api/mcp).

### Is the Penny Rounding MCP server safe to use?

Penny Rounding scores 73 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the Penny Rounding MCP server expose?

Penny Rounding exposes 3 tools: round_cash_total, rounding_impact, price_band. Their descriptions and schemas cost roughly 1,505 tokens of context every time the server is loaded.

### Does the Penny Rounding MCP server require authentication?

No. We connected to Penny Rounding without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the Penny Rounding MCP server still maintained?

Penny Rounding is still listed as active in the MCP registry. We last reached this channel on 25 September 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://penny-rounding.gumballtools.com/api/mcp
- Repository: https://github.com/bwalvoord/gumball
- Website: https://penny-rounding.gumballtools.com/
- Changelog RSS feed: https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp.xml
- Changelog JSON feed: https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp.json
- HTML version of this page: https://verifymcp.io/servers/com-gumballtools-penny-rounding/api-mcp