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	$230.38	9.431%	$252.1071	$252.11	$252.10	$252.10
Purchase #2	$83.65	7.666%	$90.0626	$90.06	$90.05	$90.10
Purchase #3	$190.72	4.806%	$199.886	$199.89	$199.90	$199.90
Purchase #4	$15.52	10.849%	$17.2038	$17.20	$17.20	$17.20
Purchase #5	$111.33	5.561%	$117.5211	$117.52	$117.50	$117.50
Purchase #6	$40.40	13.343%	$45.7906	$45.79	$45.80	$45.80
Purchase #7	$169.95	6.757%	$181.4335	$181.43	$181.45	$181.40
7 purchase totals =	$841.95		$904.0047	$904.00	$904.00	$904.00