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	$103.36	8.226%	$111.8624	$111.86	$111.85	$111.90
Purchase #2	$154.28	4.738%	$161.5898	$161.59	$161.60	$161.60
Purchase #3	$19.65	9.859%	$21.5873	$21.59	$21.60	$21.60
Purchase #4	$116.38	3.248%	$120.16	$120.16	$120.15	$120.20
Purchase #5	$150.57	7.488%	$161.8447	$161.84	$161.85	$161.80
Purchase #6	$209.65	10.406%	$231.4662	$231.47	$231.45	$231.50
Purchase #7	$12.30	9.704%	$13.4936	$13.49	$13.50	$13.50
7 purchase totals =	$766.19		$822.0040	$822.00	$822.00	$822.10