Yeah even in university in my intro-level accounting classes they said in the real world nobody cares about discrepancies less than a dollar (and that amount scales with the size of the business). I don't know if that's actually true and I wasn't an accounting major so I don't know what they said in the more advanced classes.
But if I imagine myself as a business owner I would be annoyed with my accounting firm if they spent billable hours chasing down a discrepancy of a few pennies.
Years of practice have led me to this practical wisdom:
As long as things are consistent, no one cares if you are correct. If you lose a penny in the backend calculation, and the frontend shows the amount without the penny, and the email contains the amount without the penny, and the PDF download contains the amount without the penny, no one will care that there should be a penny there.
It becomes problematic if some places are wrong and some are right, and they are not consistent. You won't get credit for being right in only some places.
As long as the error is small enough to be inconsequential, being consistent is more important than being correct.
But if I imagine myself as a business owner I would be annoyed with my accounting firm if they spent billable hours chasing down a discrepancy of a few pennies.