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	$152.77	8.581%	$165.8792	$165.88	$165.90	$165.90
Purchase #2	$146.36	10.392%	$161.5697	$161.57	$161.55	$161.60
Purchase #3	$152.47	5.263%	$160.4945	$160.49	$160.50	$160.50
Purchase #4	$205.61	8.413%	$222.908	$222.91	$222.90	$222.90
Purchase #5	$38.48	4.552%	$40.2316	$40.23	$40.25	$40.20
Purchase #6	$231.41	8.694%	$251.5288	$251.53	$251.55	$251.50
Purchase #7	$48.37	10.831%	$53.609	$53.61	$53.60	$53.60
7 purchase totals =	$975.47		$1,056.2208	$1,056.22	$1,056.25	$1,056.20