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	$165.30	9.844%	$181.5721	$181.57	$181.55	$181.60
Purchase #2	$47.89	5.717%	$50.6279	$50.63	$50.65	$50.60
Purchase #3	$183.33	13.594%	$208.2519	$208.25	$208.25	$208.30
Purchase #4	$138.91	3.438%	$143.6857	$143.69	$143.70	$143.70
Purchase #5	$161.32	5.444%	$170.1023	$170.10	$170.10	$170.10
Purchase #6	$76.34	13.377%	$86.552	$86.55	$86.55	$86.60
Purchase #7	$107.33	3.487%	$111.0726	$111.07	$111.05	$111.10
7 purchase totals =	$880.42		$951.8645	$951.86	$951.85	$952.00