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	$223.53	10.233%	$246.4038	$246.40	$246.40	$246.40
Purchase #2	$90.52	6.464%	$96.3712	$96.37	$96.35	$96.40
Purchase #3	$17.34	4.346%	$18.0936	$18.09	$18.10	$18.10
Purchase #4	$215.34	11.678%	$240.4874	$240.49	$240.50	$240.50
Purchase #5	$52.90	11.853%	$59.1702	$59.17	$59.15	$59.20
Purchase #6	$11.93	11.817%	$13.3398	$13.34	$13.35	$13.30
Purchase #7	$217.85	11.357%	$242.5912	$242.59	$242.60	$242.60
7 purchase totals =	$829.41		$916.4572	$916.45	$916.45	$916.50