Issues with float rounding pop up regularly in this forum, as well as in many others devoted to distinct programming languages. While the reasons for discrepancies observed by poster are correctly adressed here and there, practical advices are not always spot on the poster use case.
Depending on the actual context, several rounding methods can be put to work. Here's a snippet offering the most useful.
Be sure to read and understand the companion article for details: https://en.wikipedia.org/wiki/Rounding
Rounding.au3