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	$195.51	13.524%	$221.9508	$221.95	$221.95	$222.00
Purchase #2	$92.32	9.173%	$100.7885	$100.79	$100.80	$100.80
Purchase #3	$245.51	7.366%	$263.5943	$263.59	$263.60	$263.60
Purchase #4	$143.28	11.536%	$159.8088	$159.81	$159.80	$159.80
Purchase #5	$231.87	10.531%	$256.2882	$256.29	$256.30	$256.30
Purchase #6	$182.49	4.378%	$190.4794	$190.48	$190.50	$190.50
Purchase #7	$126.58	4.584%	$132.3824	$132.38	$132.40	$132.40
7 purchase totals =	$1,217.56		$1,325.2924	$1,325.29	$1,325.35	$1,325.40