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	$228.39	8.510%	$247.826	$247.83	$247.85	$247.80
Purchase #2	$105.46	13.536%	$119.7351	$119.74	$119.75	$119.70
Purchase #3	$59.54	11.436%	$66.349	$66.35	$66.35	$66.30
Purchase #4	$90.82	3.847%	$94.3138	$94.31	$94.30	$94.30
Purchase #5	$231.74	5.358%	$244.1566	$244.16	$244.15	$244.20
Purchase #6	$83.86	5.357%	$88.3524	$88.35	$88.35	$88.40
Purchase #7	$241.70	8.744%	$262.8342	$262.83	$262.85	$262.80
7 purchase totals =	$1,041.51		$1,123.5671	$1,123.57	$1,123.60	$1,123.50