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	$244.41	3.573%	$253.1428	$253.14	$253.15	$253.10
Purchase #2	$118.29	7.112%	$126.7028	$126.70	$126.70	$126.70
Purchase #3	$106.75	4.230%	$111.2655	$111.27	$111.25	$111.30
Purchase #4	$92.51	12.514%	$104.0867	$104.09	$104.10	$104.10
Purchase #5	$14.60	6.210%	$15.5067	$15.51	$15.50	$15.50
Purchase #6	$126.86	11.130%	$140.9795	$140.98	$141.00	$141.00
Purchase #7	$179.25	5.627%	$189.3364	$189.34	$189.35	$189.30
7 purchase totals =	$882.67		$941.0204	$941.03	$941.05	$941.00