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	$153.88	12.211%	$172.6703	$172.67	$172.65	$172.70
Purchase #2	$118.51	10.206%	$130.6051	$130.61	$130.60	$130.60
Purchase #3	$26.56	8.105%	$28.7127	$28.71	$28.70	$28.70
Purchase #4	$146.29	3.752%	$151.7788	$151.78	$151.80	$151.80
Purchase #5	$149.39	5.722%	$157.9381	$157.94	$157.95	$157.90
Purchase #6	$114.29	10.513%	$126.3053	$126.31	$126.30	$126.30
Purchase #7	$179.87	11.480%	$200.5191	$200.52	$200.50	$200.50
7 purchase totals =	$888.79		$968.5294	$968.54	$968.50	$968.50