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	$206.72	13.732%	$235.1068	$235.11	$235.10	$235.10
Purchase #2	$40.97	8.711%	$44.5389	$44.54	$44.55	$44.50
Purchase #3	$125.43	4.103%	$130.5764	$130.58	$130.60	$130.60
Purchase #4	$66.87	8.826%	$72.7719	$72.77	$72.75	$72.80
Purchase #5	$127.56	6.664%	$136.0606	$136.06	$136.05	$136.10
Purchase #6	$68.64	3.756%	$71.2181	$71.22	$71.20	$71.20
Purchase #7	$235.36	6.341%	$250.2842	$250.28	$250.30	$250.30
7 purchase totals =	$871.55		$940.5569	$940.56	$940.55	$940.60