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	$141.47	12.271%	$158.8298	$158.83	$158.85	$158.80
Purchase #2	$221.26	11.859%	$247.4992	$247.50	$247.50	$247.50
Purchase #3	$231.47	10.337%	$255.3971	$255.40	$255.40	$255.40
Purchase #4	$190.65	5.229%	$200.6191	$200.62	$200.60	$200.60
Purchase #5	$202.52	7.248%	$217.1986	$217.20	$217.20	$217.20
Purchase #6	$19.89	8.730%	$21.6264	$21.63	$21.65	$21.60
Purchase #7	$88.40	7.353%	$94.9001	$94.90	$94.90	$94.90
7 purchase totals =	$1,095.66		$1,196.0703	$1,196.08	$1,196.10	$1,196.00