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	$165.35	11.365%	$184.142	$184.14	$184.15	$184.10
Purchase #2	$145.93	4.810%	$152.9492	$152.95	$152.95	$152.90
Purchase #3	$131.36	4.737%	$137.5825	$137.58	$137.60	$137.60
Purchase #4	$194.72	8.111%	$210.5137	$210.51	$210.50	$210.50
Purchase #5	$180.85	10.361%	$199.5879	$199.59	$199.60	$199.60
Purchase #6	$232.88	10.180%	$256.5872	$256.59	$256.60	$256.60
Purchase #7	$151.48	5.500%	$159.8114	$159.81	$159.80	$159.80
7 purchase totals =	$1,202.57		$1,301.1739	$1,301.17	$1,301.20	$1,301.10