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	$105.37	11.142%	$117.1103	$117.11	$117.10	$117.10
Purchase #2	$20.64	7.251%	$22.1366	$22.14	$22.15	$22.10
Purchase #3	$87.32	4.113%	$90.9115	$90.91	$90.90	$90.90
Purchase #4	$169.26	9.775%	$185.8052	$185.81	$185.80	$185.80
Purchase #5	$37.70	7.383%	$40.4834	$40.48	$40.50	$40.50
Purchase #6	$112.44	3.224%	$116.0651	$116.07	$116.05	$116.10
Purchase #7	$153.91	3.660%	$159.5431	$159.54	$159.55	$159.50
7 purchase totals =	$686.64		$732.0552	$732.06	$732.05	$732.00