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	$172.52	10.152%	$190.0342	$190.03	$190.05	$190.00
Purchase #2	$32.37	4.194%	$33.7276	$33.73	$33.75	$33.70
Purchase #3	$103.26	8.177%	$111.7036	$111.70	$111.70	$111.70
Purchase #4	$57.74	6.502%	$61.4943	$61.49	$61.50	$61.50
Purchase #5	$89.54	10.730%	$99.1476	$99.15	$99.15	$99.10
Purchase #6	$73.64	12.864%	$83.113	$83.11	$83.10	$83.10
Purchase #7	$193.72	9.545%	$212.2106	$212.21	$212.20	$212.20
7 purchase totals =	$722.79		$791.4309	$791.42	$791.45	$791.30