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	$81.51	4.746%	$85.3785	$85.38	$85.40	$85.40
Purchase #2	$107.72	3.495%	$111.4848	$111.48	$111.50	$111.50
Purchase #3	$228.91	3.248%	$236.345	$236.35	$236.35	$236.30
Purchase #4	$147.40	12.430%	$165.7218	$165.72	$165.70	$165.70
Purchase #5	$239.57	9.429%	$262.1591	$262.16	$262.15	$262.20
Purchase #6	$178.86	13.196%	$202.4624	$202.46	$202.45	$202.50
Purchase #7	$233.59	13.597%	$265.3512	$265.35	$265.35	$265.40
7 purchase totals =	$1,217.56		$1,328.9028	$1,328.90	$1,328.90	$1,329.00