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	$223.67	13.499%	$253.8632	$253.86	$253.85	$253.90
Purchase #2	$146.79	12.685%	$165.4103	$165.41	$165.40	$165.40
Purchase #3	$153.65	7.266%	$164.8142	$164.81	$164.80	$164.80
Purchase #4	$226.30	5.846%	$239.5295	$239.53	$239.55	$239.50
Purchase #5	$99.34	4.697%	$104.006	$104.01	$104.00	$104.00
Purchase #6	$195.55	13.833%	$222.6004	$222.60	$222.60	$222.60
Purchase #7	$40.61	11.849%	$45.4219	$45.42	$45.40	$45.40
7 purchase totals =	$1,085.91		$1,195.6455	$1,195.64	$1,195.60	$1,195.60