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	$112.72	9.664%	$123.6133	$123.61	$123.60	$123.60
Purchase #2	$132.74	11.504%	$148.0104	$148.01	$148.00	$148.00
Purchase #3	$183.72	5.813%	$194.3996	$194.40	$194.40	$194.40
Purchase #4	$126.28	5.208%	$132.8567	$132.86	$132.85	$132.90
Purchase #5	$18.43	13.146%	$20.8528	$20.85	$20.85	$20.90
Purchase #6	$215.77	10.678%	$238.8099	$238.81	$238.80	$238.80
Purchase #7	$33.28	10.233%	$36.6855	$36.69	$36.70	$36.70
7 purchase totals =	$822.94		$895.2282	$895.23	$895.20	$895.30