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	$59.33	13.863%	$67.5549	$67.55	$67.55	$67.60
Purchase #2	$193.28	6.268%	$205.3948	$205.39	$205.40	$205.40
Purchase #3	$146.80	7.741%	$158.1638	$158.16	$158.15	$158.20
Purchase #4	$228.47	12.277%	$256.5193	$256.52	$256.50	$256.50
Purchase #5	$67.52	12.808%	$76.168	$76.17	$76.15	$76.20
Purchase #6	$171.55	10.680%	$189.8715	$189.87	$189.85	$189.90
Purchase #7	$13.43	10.551%	$14.847	$14.85	$14.85	$14.80
7 purchase totals =	$880.38		$968.5193	$968.51	$968.45	$968.60