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	$229.50	6.699%	$244.8742	$244.87	$244.85	$244.90
Purchase #2	$87.47	13.310%	$99.1123	$99.11	$99.10	$99.10
Purchase #3	$239.60	10.466%	$264.6765	$264.68	$264.70	$264.70
Purchase #4	$11.55	8.141%	$12.4903	$12.49	$12.50	$12.50
Purchase #5	$153.53	12.186%	$172.2392	$172.24	$172.25	$172.20
Purchase #6	$75.98	9.375%	$83.1031	$83.10	$83.10	$83.10
Purchase #7	$197.41	5.758%	$208.7769	$208.78	$208.80	$208.80
7 purchase totals =	$995.04		$1,085.2725	$1,085.27	$1,085.30	$1,085.30