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	$248.79	5.175%	$261.6649	$261.66	$261.65	$261.70
Purchase #2	$14.52	5.265%	$15.2845	$15.28	$15.30	$15.30
Purchase #3	$108.94	6.637%	$116.1703	$116.17	$116.15	$116.20
Purchase #4	$244.95	4.261%	$255.3873	$255.39	$255.40	$255.40
Purchase #5	$165.41	11.500%	$184.4322	$184.43	$184.45	$184.40
Purchase #6	$18.79	11.790%	$21.0053	$21.01	$21.00	$21.00
Purchase #7	$100.58	10.490%	$111.1308	$111.13	$111.15	$111.10
7 purchase totals =	$901.98		$965.0753	$965.07	$965.10	$965.10