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	$225.51	9.418%	$246.7485	$246.75	$246.75	$246.70
Purchase #2	$16.31	11.248%	$18.1445	$18.14	$18.15	$18.10
Purchase #3	$89.72	10.409%	$99.059	$99.06	$99.05	$99.10
Purchase #4	$196.43	8.198%	$212.5333	$212.53	$212.55	$212.50
Purchase #5	$172.74	13.431%	$195.9407	$195.94	$195.95	$195.90
Purchase #6	$180.72	13.833%	$205.719	$205.72	$205.70	$205.70
Purchase #7	$56.78	8.299%	$61.4922	$61.49	$61.50	$61.50
7 purchase totals =	$938.21		$1,039.6372	$1,039.63	$1,039.65	$1,039.50