# Penny Rounding

What a cash total actually rounds to now that the penny is gone.

**Why delegate it:** Four things are wrong in most explanations and each changes the answer: rounding is cash-only, applies to the total rather than each item, happens after tax, and is not free money for retailers. Money in floating point is also a bug waiting to happen.

Site: https://penny-rounding.vercel.app

## Tools

### `round_cash_total` — Round a cash total the way the post-penny rules work

Settle a transaction: exact subtotal, tax computed on that exact subtotal, then round the final total to the nearest nickel — and ONLY for cash. Card, EFT and gift-card payments stay priced to the cent, so the same basket legitimately comes to two amounts. Rounding applies to the TOTAL, never per item. A final digit of 1, 2, 6 or 7 rounds down; 3, 4, 8 or 9 rounds up. A string amount is read as dollars, a number as integer cents. Not legal or tax advice — there was no federal rounding law as of September 2026 and state law varies.

Direct endpoint: `https://penny-rounding.vercel.app/api/v1/settle`

### `rounding_impact` — What cash rounding is actually worth

Compute the mean rounding delta per cash transaction across a price list. Answers "does rounding make retailers money" with arithmetic rather than a guess: symmetric rounding nets to essentially zero by construction. Pass always-up to quantify the "just round everything up" idea, which is worth about 2 cents a sale and which no jurisdiction has adopted for retail.

Direct endpoint: `https://penny-rounding.vercel.app/api/v1/impact`

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Via the aggregator: `https://gumballtools.com/api/mcp`
Direct: `https://penny-rounding.vercel.app/api/mcp`