Wash. Rev. Code § 19.450.010
Transaction rounding—Calculation and remittance of all taxes and fees—No action constitutes violation
(1) Any person selling goods or services shall calculate and remit all taxes and fees imposed by state or municipal taxing authorities based on the sales price before any transaction rounding authorized by RCW 1.100.010.(2) No action taken in compliance with RCW 1.100.010 by any person selling goods or services constit…