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	$145.67	7.488%	$156.5778	$156.58	$156.60	$156.60
Purchase #2	$48.51	10.641%	$53.6719	$53.67	$53.65	$53.70
Purchase #3	$98.54	13.412%	$111.7562	$111.76	$111.75	$111.80
Purchase #4	$238.48	8.380%	$258.4646	$258.46	$258.45	$258.50
Purchase #5	$51.43	12.161%	$57.6844	$57.68	$57.70	$57.70
Purchase #6	$166.38	3.850%	$172.7856	$172.79	$172.80	$172.80
Purchase #7	$122.60	8.417%	$132.9192	$132.92	$132.90	$132.90
7 purchase totals =	$871.61		$943.8597	$943.86	$943.85	$944.00