Tiny but still an error: Two W2s: 40889.66 + 40598.77. TurboTax added them to 81489.00, but it should be 81488.43 rounded to 81488. How can I report this?

Not sure why you fretting over this----but each of those amounts is rounded before they are added to each other.  So......

40889.66 rounds to 40890

40598.77 rounds to 40599

Add them                   81489

So you can leave the cents off one of them to make it round right.  

Ahh, so the software rounds first. The thing that saves this argument -- round before adding -- is that's what the government does. Add the numbers (at the left side) 12 times. Add them while rounding each one, then do it again and round at the end:

• Round each 1.0 > 12.0 > 12
• Round at end 1.1 > 13.2 > 13
• Round each 2.0 > 24.0 > 24
• Round at end 1.9 > 22.8 > 23

I was fretting over it because an error is still an error, and such a difference -- whether an actual error or it's that way because of methodology -- could land you in a different tax bracket.