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	$47.33	5.185%	$49.7841	$49.78	$49.80	$49.80
Purchase #2	$190.59	4.749%	$199.6411	$199.64	$199.65	$199.60
Purchase #3	$65.69	7.506%	$70.6207	$70.62	$70.60	$70.60
Purchase #4	$141.75	7.735%	$152.7144	$152.71	$152.70	$152.70
Purchase #5	$148.47	6.547%	$158.1903	$158.19	$158.20	$158.20
Purchase #6	$164.76	11.714%	$184.06	$184.06	$184.05	$184.10
Purchase #7	$111.76	5.719%	$118.1516	$118.15	$118.15	$118.20
7 purchase totals =	$870.35		$933.1622	$933.15	$933.15	$933.20