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	$102.42	7.589%	$110.1927	$110.19	$110.20	$110.20
Purchase #2	$218.29	13.411%	$247.5649	$247.56	$247.55	$247.60
Purchase #3	$247.56	3.592%	$256.4524	$256.45	$256.45	$256.50
Purchase #4	$48.26	11.155%	$53.6434	$53.64	$53.65	$53.60
Purchase #5	$122.70	7.356%	$131.7258	$131.73	$131.75	$131.70
Purchase #6	$153.64	12.329%	$172.5823	$172.58	$172.60	$172.60
Purchase #7	$141.72	6.610%	$151.0877	$151.09	$151.10	$151.10
7 purchase totals =	$1,034.59		$1,123.2492	$1,123.24	$1,123.30	$1,123.30