Comment by matheusmoreira

Learning and using the ledger-cli accounting tool taught me a lot about this. It's incredible how messy seemingly simple things can be and how much trouble a bunch of cents can cause. Seems to be the accounting version of off-by-one errors. It is very tempting to just write them off as losses and forget about them forever.

Rounding in particular is a truly endless source of trouble and has caused me to chase after a lot of cents. Dividing up a large payment into multiple installments is the major cause of rounding in my use case. Life starts to suck the second things fail to be evenly divisible. I created an account to track gains and losses due to rounding and over time and it's adding up to quite the chunk of change.

Hilariously, the payment systems would charge me incorrect rounded up amounts and then they would refund the difference to my credit card at some undefined time in the future. Tracking and correlating all these seemingly random one or two cent transactions has got to be one of the most annoying activities I've ever learned to put up with. Not only do I have to figure out why things aren't quite adding up, I have to patch things up in the future when they fix the mistake.

Why can't these things just charge the correct amounts? For example, imagine splitting up $55.53 into four installments. That's 4x$13.8825. They could charge me 3x$13.88 + 1x$14.89. Instead they round it up to $55.56 and charge me 4x$13.89, then maybe they refund me $0.03 some unknown day in the future. It's like the systems go out of their way to be as annoying as possible. Some systems do this silly single cent refund dance in my credit card statement even though they print the exact same 3xN + 1xN+0.01 solution in the receipt. Makes absolutely no sense to me.

It's getting to the point I'm trying to avoid this nonsense by structuring purchases so the final price is evenly divisible by some common factors. I never liked the .99 cents manipulation trick but I seriously hate it now.