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	$200.94	6.576%	$214.1538	$214.15	$214.15	$214.20
Purchase #2	$222.53	10.204%	$245.237	$245.24	$245.25	$245.20
Purchase #3	$43.72	5.721%	$46.2212	$46.22	$46.20	$46.20
Purchase #4	$140.70	13.388%	$159.5369	$159.54	$159.55	$159.50
Purchase #5	$64.79	3.839%	$67.2773	$67.28	$67.30	$67.30
Purchase #6	$59.45	13.671%	$67.5774	$67.58	$67.60	$67.60
Purchase #7	$184.30	4.484%	$192.564	$192.56	$192.55	$192.60
7 purchase totals =	$916.43		$992.5676	$992.57	$992.60	$992.60