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	$227.55	12.142%	$255.1791	$255.18	$255.20	$255.20
Purchase #2	$168.70	4.626%	$176.5041	$176.50	$176.50	$176.50
Purchase #3	$134.70	12.494%	$151.5294	$151.53	$151.55	$151.50
Purchase #4	$125.66	5.719%	$132.8465	$132.85	$132.85	$132.80
Purchase #5	$136.37	10.812%	$151.1143	$151.11	$151.10	$151.10
Purchase #6	$76.85	11.531%	$85.7116	$85.71	$85.70	$85.70
Purchase #7	$111.32	10.123%	$122.5889	$122.59	$122.60	$122.60
7 purchase totals =	$981.15		$1,075.4739	$1,075.47	$1,075.50	$1,075.40