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	$95.35	11.205%	$106.034	$106.03	$106.05	$106.00
Purchase #2	$40.39	13.106%	$45.6835	$45.68	$45.70	$45.70
Purchase #3	$59.60	13.779%	$67.8123	$67.81	$67.80	$67.80
Purchase #4	$46.77	6.317%	$49.7245	$49.72	$49.70	$49.70
Purchase #5	$104.35	6.772%	$111.4166	$111.42	$111.40	$111.40
Purchase #6	$130.75	6.421%	$139.1455	$139.15	$139.15	$139.10
Purchase #7	$32.83	3.268%	$33.9029	$33.90	$33.90	$33.90
7 purchase totals =	$510.04		$553.7193	$553.71	$553.70	$553.60