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	$208.63	9.106%	$227.6278	$227.63	$227.65	$227.60
Purchase #2	$70.59	10.813%	$78.2229	$78.22	$78.20	$78.20
Purchase #3	$143.51	5.438%	$151.3141	$151.31	$151.30	$151.30
Purchase #4	$37.96	5.564%	$40.0721	$40.07	$40.05	$40.10
Purchase #5	$44.26	3.335%	$45.7361	$45.74	$45.75	$45.70
Purchase #6	$157.73	5.421%	$166.2805	$166.28	$166.30	$166.30
Purchase #7	$169.93	12.164%	$190.6003	$190.60	$190.60	$190.60
7 purchase totals =	$832.61		$899.8538	$899.85	$899.85	$899.80