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	$231.90	9.287%	$253.4366	$253.44	$253.45	$253.40
Purchase #2	$91.58	9.629%	$100.3982	$100.40	$100.40	$100.40
Purchase #3	$128.70	13.756%	$146.404	$146.40	$146.40	$146.40
Purchase #4	$201.31	6.608%	$214.6126	$214.61	$214.60	$214.60
Purchase #5	$59.46	5.190%	$62.546	$62.55	$62.55	$62.50
Purchase #6	$214.82	4.580%	$224.6588	$224.66	$224.65	$224.70
Purchase #7	$230.89	9.365%	$252.5128	$252.51	$252.50	$252.50
7 purchase totals =	$1,158.66		$1,254.5690	$1,254.57	$1,254.55	$1,254.50