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	$50.72	7.313%	$54.4292	$54.43	$54.45	$54.40
Purchase #2	$52.50	13.428%	$59.5497	$59.55	$59.55	$59.50
Purchase #3	$161.97	6.628%	$172.7054	$172.71	$172.70	$172.70
Purchase #4	$118.64	9.799%	$130.2655	$130.27	$130.25	$130.30
Purchase #5	$32.48	12.561%	$36.5598	$36.56	$36.55	$36.60
Purchase #6	$225.87	9.246%	$246.7539	$246.75	$246.75	$246.80
Purchase #7	$53.78	3.541%	$55.6843	$55.68	$55.70	$55.70
7 purchase totals =	$695.96		$755.9478	$755.95	$755.95	$756.00