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	$143.61	5.298%	$151.2185	$151.22	$151.20	$151.20
Purchase #2	$204.45	10.487%	$225.8907	$225.89	$225.90	$225.90
Purchase #3	$55.35	9.806%	$60.7776	$60.78	$60.80	$60.80
Purchase #4	$134.61	9.152%	$146.9295	$146.93	$146.95	$146.90
Purchase #5	$45.70	6.707%	$48.7651	$48.77	$48.75	$48.80
Purchase #6	$222.50	4.750%	$233.0688	$233.07	$233.05	$233.10
Purchase #7	$248.85	6.194%	$264.2638	$264.26	$264.25	$264.30
7 purchase totals =	$1,055.07		$1,130.9140	$1,130.92	$1,130.90	$1,131.00