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	$36.64	3.271%	$37.8385	$37.84	$37.85	$37.80
Purchase #2	$21.49	5.562%	$22.6853	$22.69	$22.70	$22.70
Purchase #3	$237.29	7.854%	$255.9268	$255.93	$255.95	$255.90
Purchase #4	$141.26	4.399%	$147.474	$147.47	$147.45	$147.50
Purchase #5	$138.44	10.290%	$152.6855	$152.69	$152.70	$152.70
Purchase #6	$231.31	10.621%	$255.8774	$255.88	$255.90	$255.90
Purchase #7	$148.47	11.492%	$165.5322	$165.53	$165.55	$165.50
7 purchase totals =	$954.90		$1,038.0197	$1,038.03	$1,038.10	$1,038.00