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	$200.33	11.250%	$222.8671	$222.87	$222.85	$222.90
Purchase #2	$83.96	8.224%	$90.8649	$90.86	$90.85	$90.90
Purchase #3	$234.76	13.683%	$266.8822	$266.88	$266.90	$266.90
Purchase #4	$203.92	8.645%	$221.5489	$221.55	$221.55	$221.50
Purchase #5	$231.89	10.390%	$255.9834	$255.98	$256.00	$256.00
Purchase #6	$118.70	11.638%	$132.5143	$132.51	$132.50	$132.50
Purchase #7	$160.96	9.199%	$175.7667	$175.77	$175.75	$175.80
7 purchase totals =	$1,234.52		$1,366.4275	$1,366.42	$1,366.40	$1,366.50