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	$146.57	4.318%	$152.8989	$152.90	$152.90	$152.90
Purchase #2	$118.67	10.503%	$131.1339	$131.13	$131.15	$131.10
Purchase #3	$37.97	11.671%	$42.4015	$42.40	$42.40	$42.40
Purchase #4	$32.27	8.296%	$34.9471	$34.95	$34.95	$34.90
Purchase #5	$75.94	11.481%	$84.6587	$84.66	$84.65	$84.70
Purchase #6	$214.43	13.575%	$243.5389	$243.54	$243.55	$243.50
Purchase #7	$37.52	5.357%	$39.5299	$39.53	$39.55	$39.50
7 purchase totals =	$663.37		$729.1089	$729.11	$729.15	$729.00