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	$218.52	12.484%	$245.8	$245.80	$245.80	$245.80
Purchase #2	$40.70	4.619%	$42.5799	$42.58	$42.60	$42.60
Purchase #3	$151.82	6.498%	$161.6853	$161.69	$161.70	$161.70
Purchase #4	$55.77	6.794%	$59.559	$59.56	$59.55	$59.60
Purchase #5	$140.82	8.496%	$152.7841	$152.78	$152.80	$152.80
Purchase #6	$246.69	12.698%	$278.0147	$278.01	$278.00	$278.00
Purchase #7	$62.85	5.320%	$66.1936	$66.19	$66.20	$66.20
7 purchase totals =	$917.17		$1,006.6166	$1,006.61	$1,006.65	$1,006.70