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	$58.83	11.470%	$65.5778	$65.58	$65.60	$65.60
Purchase #2	$81.88	12.464%	$92.0855	$92.09	$92.10	$92.10
Purchase #3	$192.72	12.318%	$216.4592	$216.46	$216.45	$216.50
Purchase #4	$38.80	5.239%	$40.8327	$40.83	$40.85	$40.80
Purchase #5	$237.71	4.118%	$247.4989	$247.50	$247.50	$247.50
Purchase #6	$77.67	5.383%	$81.851	$81.85	$81.85	$81.90
Purchase #7	$175.57	8.496%	$190.4864	$190.49	$190.50	$190.50
7 purchase totals =	$863.18		$934.7915	$934.80	$934.85	$934.90