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	$210.65	5.735%	$222.7308	$222.73	$222.75	$222.70
Purchase #2	$147.71	7.773%	$159.1915	$159.19	$159.20	$159.20
Purchase #3	$140.47	9.352%	$153.6068	$153.61	$153.60	$153.60
Purchase #4	$152.41	13.277%	$172.6455	$172.65	$172.65	$172.60
Purchase #5	$121.34	8.626%	$131.8068	$131.81	$131.80	$131.80
Purchase #6	$191.95	13.244%	$217.3719	$217.37	$217.35	$217.40
Purchase #7	$200.45	12.485%	$225.4762	$225.48	$225.50	$225.50
7 purchase totals =	$1,164.98		$1,282.8295	$1,282.84	$1,282.85	$1,282.80