Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$36.51	10.375%	$40.2979	$40.30	$40.30	$40.30
Purchase #2	$223.77	6.676%	$238.7089	$238.71	$238.70	$238.70
Purchase #3	$154.81	8.357%	$167.7475	$167.75	$167.75	$167.70
Purchase #4	$126.32	9.548%	$138.381	$138.38	$138.40	$138.40
Purchase #5	$192.32	8.613%	$208.8845	$208.88	$208.90	$208.90
Purchase #6	$103.26	8.396%	$111.9297	$111.93	$111.95	$111.90
Purchase #7	$187.73	10.856%	$208.11	$208.11	$208.10	$208.10
7 purchase totals =	$1,024.72		$1,114.0595	$1,114.06	$1,114.10	$1,114.00