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	$237.51	7.544%	$255.4278	$255.43	$255.45	$255.40
Purchase #2	$119.34	12.365%	$134.0964	$134.10	$134.10	$134.10
Purchase #3	$48.68	3.590%	$50.4276	$50.43	$50.45	$50.40
Purchase #4	$216.93	10.456%	$239.6122	$239.61	$239.60	$239.60
Purchase #5	$137.71	10.448%	$152.0979	$152.10	$152.10	$152.10
Purchase #6	$187.67	5.749%	$198.4591	$198.46	$198.45	$198.50
Purchase #7	$66.77	4.487%	$69.766	$69.77	$69.75	$69.80
7 purchase totals =	$1,014.61		$1,099.8870	$1,099.90	$1,099.90	$1,099.90