The most memorable math class I ever had in school saw a surprise test. It was simple math, but big, awkward numbers, and lots of them. The teacher told us that we would not have time to calculate them all (and calculators - to be honest, had not been invented yet). He told us that nearly all the math we would ever do in life would be used to make a decision. The result would direct us to a "yes" or a "no". So, if we were pressed for time, a close guess would probably result in the correct decision. The purpose of the test was for us to guess at the answer. If our guess was within 10% of the correct answer, we would get the mark.
This logic is very prevalent in piloting. You'll need to make many decisions, most usually, do I have enough fuel to get there? The good guess, with a bit of conservatism, will be adequate.
I do not imagine a situation where based on the groundspeed of a GA aircraft, there is a need to know the distance covered to within 1/100 of a mile. For my experience the nearest mile, or 5% for greater distances has met the need every time. That said, during training and exams, the questions might force greater precision, as you choose the best of two possible multiple choice answers. Know the theory, but know when to apply it too!