It is not really anything to do with computers and floating point... you can't give precise answers to quite a few real-world questions, including calculating taxes, no matter how hard you try.
For example, here is an easy question:
If I want to have $1000 in a money jar for Christmas, every Christmas, how much do I need to put in the jar each week?
Any takers to not use a pesky, imprecise, error-prone computer to give a precise answer?
Something better than the obvious (and very practical) $20 per week?