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	$150.61	4.552%	$157.4658	$157.47	$157.45	$157.50
Purchase #2	$226.66	11.374%	$252.4403	$252.44	$252.45	$252.40
Purchase #3	$103.60	7.230%	$111.0903	$111.09	$111.10	$111.10
Purchase #4	$193.50	12.415%	$217.523	$217.52	$217.50	$217.50
Purchase #5	$247.65	12.849%	$279.4705	$279.47	$279.45	$279.50
Purchase #6	$56.34	6.403%	$59.9475	$59.95	$59.95	$59.90
Purchase #7	$178.83	12.252%	$200.7403	$200.74	$200.75	$200.70
7 purchase totals =	$1,157.19		$1,278.6777	$1,278.68	$1,278.65	$1,278.60