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	$196.89	12.697%	$221.8891	$221.89	$221.90	$221.90
Purchase #2	$32.33	13.149%	$36.5811	$36.58	$36.60	$36.60
Purchase #3	$235.54	3.792%	$244.4717	$244.47	$244.45	$244.50
Purchase #4	$25.39	6.824%	$27.1226	$27.12	$27.10	$27.10
Purchase #5	$124.56	10.758%	$137.9602	$137.96	$137.95	$138.00
Purchase #6	$121.36	8.529%	$131.7108	$131.71	$131.70	$131.70
Purchase #7	$95.69	13.733%	$108.8311	$108.83	$108.85	$108.80
7 purchase totals =	$831.76		$908.5666	$908.56	$908.55	$908.60