While the instructions for this form may give that particular rounding method, the official IRS regulations allow rounding of each entry, as long as the rounding method is consistent.
With the millions of people who use TurboTax and the intense scrutiny that the program goes through to be approved by the IRS, the IRS would have certainly already had something to say about this to TurboTax if it were a problem. It is not a problem, never has been.
