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	$80.64	13.161%	$91.253	$91.25	$91.25	$91.30
Purchase #2	$112.25	13.848%	$127.7944	$127.79	$127.80	$127.80
Purchase #3	$10.64	13.475%	$12.0737	$12.07	$12.05	$12.10
Purchase #4	$67.51	7.773%	$72.7576	$72.76	$72.75	$72.80
Purchase #5	$230.41	7.262%	$247.1424	$247.14	$247.15	$247.10
Purchase #6	$167.66	12.473%	$188.5722	$188.57	$188.55	$188.60
Purchase #7	$22.52	4.869%	$23.6165	$23.62	$23.60	$23.60
7 purchase totals =	$691.63		$763.2098	$763.20	$763.15	$763.30