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	$246.34	3.403%	$254.723	$254.72	$254.70	$254.70
Purchase #2	$97.26	8.724%	$105.745	$105.75	$105.75	$105.70
Purchase #3	$47.72	13.807%	$54.3087	$54.31	$54.30	$54.30
Purchase #4	$134.99	8.817%	$146.8921	$146.89	$146.90	$146.90
Purchase #5	$128.69	11.323%	$143.2616	$143.26	$143.25	$143.30
Purchase #6	$47.31	6.263%	$50.273	$50.27	$50.25	$50.30
Purchase #7	$161.57	6.746%	$172.4695	$172.47	$172.45	$172.50
7 purchase totals =	$863.88		$927.6729	$927.67	$927.60	$927.70