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	$219.66	4.188%	$228.8594	$228.86	$228.85	$228.90
Purchase #2	$55.86	7.213%	$59.8892	$59.89	$59.90	$59.90
Purchase #3	$235.81	10.141%	$259.7235	$259.72	$259.70	$259.70
Purchase #4	$39.81	12.828%	$44.9168	$44.92	$44.90	$44.90
Purchase #5	$32.68	5.546%	$34.4924	$34.49	$34.50	$34.50
Purchase #6	$199.28	11.733%	$222.6615	$222.66	$222.65	$222.70
Purchase #7	$10.71	10.861%	$11.8732	$11.87	$11.85	$11.90
7 purchase totals =	$793.81		$862.4160	$862.41	$862.35	$862.50