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	$204.41	12.756%	$230.4845	$230.48	$230.50	$230.50
Purchase #2	$227.33	12.357%	$255.4212	$255.42	$255.40	$255.40
Purchase #3	$234.74	9.806%	$257.7586	$257.76	$257.75	$257.80
Purchase #4	$112.36	12.823%	$126.7679	$126.77	$126.75	$126.80
Purchase #5	$227.43	12.512%	$255.886	$255.89	$255.90	$255.90
Purchase #6	$176.73	7.735%	$190.4001	$190.40	$190.40	$190.40
Purchase #7	$59.41	13.856%	$67.6418	$67.64	$67.65	$67.60
7 purchase totals =	$1,242.41		$1,384.3601	$1,384.36	$1,384.35	$1,384.40