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	$96.31	9.185%	$105.1561	$105.16	$105.15	$105.20
Purchase #2	$245.95	11.750%	$274.8491	$274.85	$274.85	$274.80
Purchase #3	$28.25	12.820%	$31.8717	$31.87	$31.85	$31.90
Purchase #4	$12.46	8.704%	$13.5445	$13.54	$13.55	$13.50
Purchase #5	$132.45	8.491%	$143.6963	$143.70	$143.70	$143.70
Purchase #6	$159.61	11.265%	$177.5901	$177.59	$177.60	$177.60
Purchase #7	$111.69	12.650%	$125.8188	$125.82	$125.80	$125.80
7 purchase totals =	$786.72		$872.5266	$872.53	$872.50	$872.50