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	$111.94	7.757%	$120.6232	$120.62	$120.60	$120.60
Purchase #2	$48.64	4.363%	$50.7622	$50.76	$50.75	$50.80
Purchase #3	$64.65	13.168%	$73.1631	$73.16	$73.15	$73.20
Purchase #4	$5.39	3.341%	$5.5701	$5.57	$5.55	$5.60
Purchase #5	$66.64	11.799%	$74.5029	$74.50	$74.50	$74.50
Purchase #6	$65.71	10.745%	$72.7705	$72.77	$72.75	$72.80
Purchase #7	$228.81	11.832%	$255.8828	$255.88	$255.90	$255.90
7 purchase totals =	$591.78		$653.2748	$653.26	$653.20	$653.40