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	$243.66	3.220%	$251.5059	$251.51	$251.50	$251.50
Purchase #2	$158.76	8.779%	$172.6975	$172.70	$172.70	$172.70
Purchase #3	$72.99	5.726%	$77.1694	$77.17	$77.15	$77.20
Purchase #4	$182.55	9.117%	$199.1931	$199.19	$199.20	$199.20
Purchase #5	$58.81	5.230%	$61.8858	$61.89	$61.90	$61.90
Purchase #6	$83.33	8.457%	$90.3772	$90.38	$90.40	$90.40
Purchase #7	$230.38	5.728%	$243.5762	$243.58	$243.60	$243.60
7 purchase totals =	$1,030.48		$1,096.4051	$1,096.42	$1,096.45	$1,096.50