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	$169.34	11.501%	$188.8158	$188.82	$188.80	$188.80
Purchase #2	$118.90	9.505%	$130.2014	$130.20	$130.20	$130.20
Purchase #3	$23.57	5.208%	$24.7975	$24.80	$24.80	$24.80
Purchase #4	$132.30	10.702%	$146.4587	$146.46	$146.45	$146.50
Purchase #5	$206.44	3.139%	$212.9202	$212.92	$212.90	$212.90
Purchase #6	$157.83	9.297%	$172.5035	$172.50	$172.50	$172.50
Purchase #7	$16.63	11.767%	$18.5869	$18.59	$18.60	$18.60
7 purchase totals =	$825.01		$894.2840	$894.29	$894.25	$894.30