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	$130.88	9.313%	$143.0689	$143.07	$143.05	$143.10
Purchase #2	$133.29	13.679%	$151.5227	$151.52	$151.50	$151.50
Purchase #3	$24.39	8.274%	$26.408	$26.41	$26.40	$26.40
Purchase #4	$54.79	8.757%	$59.588	$59.59	$59.60	$59.60
Purchase #5	$146.61	7.468%	$157.5588	$157.56	$157.55	$157.60
Purchase #6	$59.54	13.310%	$67.4648	$67.46	$67.45	$67.50
Purchase #7	$217.29	8.672%	$236.1334	$236.13	$236.15	$236.10
7 purchase totals =	$766.79		$841.7446	$841.74	$841.70	$841.80