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	$222.38	6.540%	$236.9237	$236.92	$236.90	$236.90
Purchase #2	$30.59	3.178%	$31.5622	$31.56	$31.55	$31.60
Purchase #3	$104.43	9.701%	$114.5608	$114.56	$114.55	$114.60
Purchase #4	$11.45	11.198%	$12.7322	$12.73	$12.75	$12.70
Purchase #5	$83.77	8.208%	$90.6458	$90.65	$90.65	$90.60
Purchase #6	$42.76	12.359%	$48.0447	$48.04	$48.05	$48.00
Purchase #7	$177.71	5.733%	$187.8981	$187.90	$187.90	$187.90
7 purchase totals =	$673.09		$722.3675	$722.36	$722.35	$722.30