The actual problem had nothing to do with OpenZepllin, but I must admit that I didn't know about the know decimal limitations.
@GoodVibrations noted that if I displayed everything WEI, the math was correct (and I updated the question with those numbers). So it was converting WEI to a decimal that was the problem.
The immediate issue appears to be that you are expecting non-integer results from your equation when using integers in Solidity.
As other people have commented, in Solidity when dealing with integers, 2/100 = 0
In Solidity, division rounds towards zero.
Remix is great to quickly test ...