No need to invent a divide between "computer people" and "tax people," whoever they are. Maybe the IRS allows small errors because bugs attributable to floating-point precision are too hard to fix.
...while financial institutions send reports to clients and the IRS that have the totals rounded only at the end, meaning the things that are supposed to match don't and can't.
Even though they are both in dollars, they are not consistent even to the nearest dollar.