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	$190.62	13.602%	$216.5481	$216.55	$216.55	$216.50
Purchase #2	$211.72	7.429%	$227.4487	$227.45	$227.45	$227.40
Purchase #3	$141.74	11.836%	$158.5163	$158.52	$158.50	$158.50
Purchase #4	$107.87	3.392%	$111.529	$111.53	$111.55	$111.50
Purchase #5	$71.99	8.393%	$78.0321	$78.03	$78.05	$78.00
Purchase #6	$117.43	4.526%	$122.7449	$122.74	$122.75	$122.70
Purchase #7	$240.67	4.164%	$250.6915	$250.69	$250.70	$250.70
7 purchase totals =	$1,082.04		$1,165.5106	$1,165.51	$1,165.55	$1,165.30