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	$233.96	9.324%	$255.7744	$255.77	$255.75	$255.80
Purchase #2	$29.67	6.466%	$31.5885	$31.59	$31.60	$31.60
Purchase #3	$218.42	8.369%	$236.6996	$236.70	$236.70	$236.70
Purchase #4	$144.43	5.159%	$151.8811	$151.88	$151.90	$151.90
Purchase #5	$37.26	9.848%	$40.9294	$40.93	$40.95	$40.90
Purchase #6	$38.66	3.551%	$40.0328	$40.03	$40.05	$40.00
Purchase #7	$27.69	6.469%	$29.4813	$29.48	$29.50	$29.50
7 purchase totals =	$730.09		$786.3871	$786.38	$786.45	$786.40