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	$231.42	10.527%	$255.7816	$255.78	$255.80	$255.80
Purchase #2	$206.48	7.183%	$221.3115	$221.31	$221.30	$221.30
Purchase #3	$131.81	7.361%	$141.5125	$141.51	$141.50	$141.50
Purchase #4	$224.95	6.175%	$238.8407	$238.84	$238.85	$238.80
Purchase #5	$42.81	11.175%	$47.594	$47.59	$47.60	$47.60
Purchase #6	$180.97	9.706%	$198.5349	$198.53	$198.55	$198.50
Purchase #7	$10.35	8.688%	$11.2492	$11.25	$11.25	$11.20
7 purchase totals =	$1,028.79		$1,114.8244	$1,114.81	$1,114.85	$1,114.70