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	$93.71	6.146%	$99.4694	$99.47	$99.45	$99.50
Purchase #2	$168.86	5.495%	$178.1389	$178.14	$178.15	$178.10
Purchase #3	$199.95	4.111%	$208.1699	$208.17	$208.15	$208.20
Purchase #4	$125.63	9.650%	$137.7533	$137.75	$137.75	$137.80
Purchase #5	$60.86	8.619%	$66.1055	$66.11	$66.10	$66.10
Purchase #6	$207.39	11.688%	$231.6297	$231.63	$231.65	$231.60
Purchase #7	$237.33	5.653%	$250.7463	$250.75	$250.75	$250.70
7 purchase totals =	$1,093.73		$1,172.0130	$1,172.02	$1,172.00	$1,172.00