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	$65.79	3.222%	$67.9098	$67.91	$67.90	$67.90
Purchase #2	$22.92	8.717%	$24.9179	$24.92	$24.90	$24.90
Purchase #3	$157.89	4.789%	$165.4514	$165.45	$165.45	$165.50
Purchase #4	$17.34	4.527%	$18.125	$18.13	$18.15	$18.10
Purchase #5	$238.67	6.362%	$253.8542	$253.85	$253.85	$253.90
Purchase #6	$175.86	11.218%	$195.588	$195.59	$195.60	$195.60
Purchase #7	$20.51	4.873%	$21.5095	$21.51	$21.50	$21.50
7 purchase totals =	$698.98		$747.3558	$747.36	$747.35	$747.40