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	$9.41	12.766%	$10.6113	$10.61	$10.60	$10.60
Purchase #2	$193.70	12.108%	$217.1532	$217.15	$217.15	$217.20
Purchase #3	$210.81	8.503%	$228.7352	$228.74	$228.75	$228.70
Purchase #4	$195.31	9.816%	$214.4816	$214.48	$214.50	$214.50
Purchase #5	$100.38	10.714%	$111.1347	$111.13	$111.15	$111.10
Purchase #6	$227.82	13.872%	$259.4232	$259.42	$259.40	$259.40
Purchase #7	$16.74	9.345%	$18.3044	$18.30	$18.30	$18.30
7 purchase totals =	$954.17		$1,059.8436	$1,059.83	$1,059.85	$1,059.80