RSU is reported on your W-2. It's figured by taking gross number of shares vesting * per share FMV at vesting date.
Your per share fair market value (FMV) for the stock is the same per share figure your employer used to calculate the compensation and that's the per share figure you'll use when the sale is reported to you.
If you are worrying about somehow not being able to enter the taxes paid with the cash raised from the stock sold "for taxes", then I know you are making the mistake of using the wrong basis to report the sale and seeing your tax liability go up when you do. The answer isn't to somehow report the withheld taxes again - they are already included on your W-2 and you can't deduct them again, the answer is to use the correct basis when reporting the sale.
As TurboTaxCherylW, EA, MsTax pointed out your correct per share basis is the same as the per share "fair market value" used by your employer to determine the compensation created by the vesting.
Enter the 1099-B exactly as it reads and then click the blue "I'll enter additional info on my own" button. On the next page enter the correct basis in the "Corrected cost basis" box. The correct basis is: (# of shares sold) x (per share basis for that lot.)
(SINCE THE DEVELOPERS CHANGE THE SECURITY SALE INTERVIEW EVERY SINGLE YEAR I'LL NOTE THAT THIS ANSWER'S DIRECTIONS ON HOW TO CORRECT THE BASIS FOR THE SALE PERTAINS TO THE 2016 INCOME TAX YEAR. I'M SURE THAT THE INTERVIEW WILL CHANGE IN THE YEARS AFTER THAT.)