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	$163.36	10.323%	$180.2237	$180.22	$180.20	$180.20
Purchase #2	$154.72	11.500%	$172.5128	$172.51	$172.50	$172.50
Purchase #3	$43.51	11.344%	$48.4458	$48.45	$48.45	$48.40
Purchase #4	$123.54	11.345%	$137.5556	$137.56	$137.55	$137.60
Purchase #5	$72.83	3.803%	$75.5997	$75.60	$75.60	$75.60
Purchase #6	$234.70	13.284%	$265.8775	$265.88	$265.90	$265.90
Purchase #7	$228.84	13.688%	$260.1636	$260.16	$260.15	$260.20
7 purchase totals =	$1,021.50		$1,140.3787	$1,140.38	$1,140.35	$1,140.40