Precision?

Quite common in accounting, the accounting equation must balance, it's like a checksum

Yes, OP started the sentence with that. But, you do make me wonder if floating-point imprecision would eventually lead to material issues...

I can see of two main ways were such imprecision can have negative effects even if small.

1- As mentioned, even if pennies, it breaks integrity checks. Which may cause for them to be ignored, which can cause real integrity issues to be ignored if by coincidence they are small.

2- There was an article about this on hn recently, but, although science values dropping excess precision in an argument in favour of not inventing precision that isn't there, sometimes more digit precision can transmit information about the calculation of the numbers, for example we see a number 1.47528, whe can be fairly certain it is 1/7th of something. If we see 1.48, less so. A simpler example would be a single cent error leading to an X.99 value which is semantically different from a round one.

The penny doesn't matter but being off by a cent can mean there are serious problems in the workflow.