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	$99.77	12.149%	$111.8911	$111.89	$111.90	$111.90
Purchase #2	$200.88	13.530%	$228.0591	$228.06	$228.05	$228.10
Purchase #3	$143.39	6.575%	$152.8179	$152.82	$152.80	$152.80
Purchase #4	$214.64	10.313%	$236.7758	$236.78	$236.80	$236.80
Purchase #5	$165.35	11.698%	$184.6926	$184.69	$184.70	$184.70
Purchase #6	$168.92	12.610%	$190.2208	$190.22	$190.20	$190.20
Purchase #7	$151.96	6.582%	$161.962	$161.96	$161.95	$162.00
7 purchase totals =	$1,144.91		$1,266.4193	$1,266.42	$1,266.40	$1,266.50