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	$197.81	7.370%	$212.3886	$212.39	$212.40	$212.40
Purchase #2	$38.41	3.352%	$39.6975	$39.70	$39.70	$39.70
Purchase #3	$179.64	9.358%	$196.4507	$196.45	$196.45	$196.50
Purchase #4	$108.78	10.782%	$120.5087	$120.51	$120.50	$120.50
Purchase #5	$48.31	13.719%	$54.9376	$54.94	$54.95	$54.90
Purchase #6	$104.95	11.634%	$117.1599	$117.16	$117.15	$117.20
Purchase #7	$212.90	5.386%	$224.3668	$224.37	$224.35	$224.40
7 purchase totals =	$890.80		$965.5098	$965.52	$965.50	$965.60