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	$196.98	4.283%	$205.4167	$205.42	$205.40	$205.40
Purchase #2	$211.81	6.251%	$225.0502	$225.05	$225.05	$225.10
Purchase #3	$233.61	9.527%	$255.866	$255.87	$255.85	$255.90
Purchase #4	$199.76	8.806%	$217.3509	$217.35	$217.35	$217.40
Purchase #5	$188.68	6.310%	$200.5857	$200.59	$200.60	$200.60
Purchase #6	$62.67	13.517%	$71.1411	$71.14	$71.15	$71.10
Purchase #7	$44.44	8.779%	$48.3414	$48.34	$48.35	$48.30
7 purchase totals =	$1,137.95		$1,223.7520	$1,223.76	$1,223.75	$1,223.80