Bingo. While growing up in the '70s, my parents were often small businessmen, or running the business affairs of e.g. groups of doctors. More than one I can remember them spending quite a while tracking down a less than $1 discrepancy in the books they necessarily kept manually, for just that reason. (They moved to doing by computer in the '80s, of course.)
In a lot of software engineering, Good Enough really is good enough. But a 5 cent discrepancy between what you actually have and what you thought you had need to be treated as seriously as a $5 million discrepancy.