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	$65.58	11.142%	$72.8869	$72.89	$72.90	$72.90
Purchase #2	$152.82	9.154%	$166.8091	$166.81	$166.80	$166.80
Purchase #3	$59.34	3.573%	$61.4602	$61.46	$61.45	$61.50
Purchase #4	$152.74	5.161%	$160.6229	$160.62	$160.60	$160.60
Purchase #5	$87.68	8.406%	$95.0504	$95.05	$95.05	$95.10
Purchase #6	$127.41	11.810%	$142.4571	$142.46	$142.45	$142.50
Purchase #7	$37.44	4.828%	$39.2476	$39.25	$39.25	$39.20
7 purchase totals =	$683.01		$738.5342	$738.54	$738.50	$738.60