26 USC § 6313
Fractional parts of a cent
October 30, 2020
In the payment of any tax imposed by this title, a fractional part of a cent shall be disregarded unless it amounts to one-half cent or more, in which case it shall be increased to 1 cent.
Amendments
1976—Pub. L. 94–455 struck out "not payable by stamp" after "title".