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	$149.59	3.727%	$155.1652	$155.17	$155.15	$155.20
Purchase #2	$155.35	11.619%	$173.4001	$173.40	$173.40	$173.40
Purchase #3	$246.85	4.863%	$258.8543	$258.85	$258.85	$258.90
Purchase #4	$99.57	11.122%	$110.6442	$110.64	$110.65	$110.60
Purchase #5	$58.28	5.410%	$61.4329	$61.43	$61.45	$61.40
Purchase #6	$146.42	9.170%	$159.8467	$159.85	$159.85	$159.80
Purchase #7	$159.60	5.604%	$168.544	$168.54	$168.55	$168.50
7 purchase totals =	$1,015.66		$1,087.8874	$1,087.88	$1,087.90	$1,087.80