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	$224.90	12.612%	$253.2644	$253.26	$253.25	$253.30
Purchase #2	$225.37	3.806%	$233.9476	$233.95	$233.95	$233.90
Purchase #3	$40.48	11.406%	$45.0971	$45.10	$45.10	$45.10
Purchase #4	$196.60	12.734%	$221.635	$221.64	$221.65	$221.60
Purchase #5	$92.43	11.294%	$102.869	$102.87	$102.85	$102.90
Purchase #6	$126.45	3.660%	$131.0781	$131.08	$131.10	$131.10
Purchase #7	$226.71	13.337%	$256.9463	$256.95	$256.95	$256.90
7 purchase totals =	$1,132.94		$1,244.8375	$1,244.85	$1,244.85	$1,244.80