Has anyone come upon rounding errors when doing math calculation and in particular to a cost being multiplied by a markup

I�m an Engineer, but alas, in this era of post Harvey Weinstein it�s probably no longer appropriate to post a link to the joke. But when I was a student a few decades ago there was a joke with a punch line

�So? I�ll be close enough for all practical purposes.�

The punch line is googleable.