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	$218.48	9.135%	$238.4381	$238.44	$238.45	$238.40
Purchase #2	$79.93	13.531%	$90.7453	$90.75	$90.75	$90.70
Purchase #3	$13.37	6.271%	$14.2084	$14.21	$14.20	$14.20
Purchase #4	$29.39	7.233%	$31.5158	$31.52	$31.50	$31.50
Purchase #5	$151.50	5.325%	$159.5674	$159.57	$159.55	$159.60
Purchase #6	$171.39	9.529%	$187.7218	$187.72	$187.70	$187.70
Purchase #7	$132.61	12.176%	$148.7566	$148.76	$148.75	$148.80
7 purchase totals =	$796.67		$870.9534	$870.97	$870.90	$870.90