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	$221.77	13.219%	$251.0858	$251.09	$251.10	$251.10
Purchase #2	$228.76	12.130%	$256.5086	$256.51	$256.50	$256.50
Purchase #3	$234.78	11.651%	$262.1342	$262.13	$262.15	$262.10
Purchase #4	$111.79	4.602%	$116.9346	$116.93	$116.95	$116.90
Purchase #5	$17.44	11.145%	$19.3837	$19.38	$19.40	$19.40
Purchase #6	$156.91	5.485%	$165.5165	$165.52	$165.50	$165.50
Purchase #7	$169.92	7.564%	$182.7727	$182.77	$182.75	$182.80
7 purchase totals =	$1,141.37		$1,254.3361	$1,254.33	$1,254.35	$1,254.30