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	$32.37	4.828%	$33.9328	$33.93	$33.95	$33.90
Purchase #2	$36.29	12.238%	$40.7312	$40.73	$40.75	$40.70
Purchase #3	$73.85	4.741%	$77.3512	$77.35	$77.35	$77.40
Purchase #4	$140.88	11.137%	$156.5698	$156.57	$156.55	$156.60
Purchase #5	$89.41	6.356%	$95.0929	$95.09	$95.10	$95.10
Purchase #6	$85.67	3.485%	$88.6556	$88.66	$88.65	$88.70
Purchase #7	$17.55	3.233%	$18.1174	$18.12	$18.10	$18.10
7 purchase totals =	$476.02		$510.4509	$510.45	$510.45	$510.50