So what you're saying is, don't round anything until you have your answer, then round the display value?
That makes sense.
I actually noticed extensions (EP cost) had to be floor rounded (e.g. cut off the decimals). One the things I still need to do is take a neuro-injection date into account, and see if the answer matches the in-game free EP value.
Random fun fact; the item with the highest CPU usage in-game is the Niani interference module with 99.00 CPU usage. Notice the two decimal precision.