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	$105.54	13.313%	$119.5905	$119.59	$119.60	$119.60
Purchase #2	$116.73	4.179%	$121.6081	$121.61	$121.60	$121.60
Purchase #3	$83.35	10.622%	$92.2034	$92.20	$92.20	$92.20
Purchase #4	$157.82	7.182%	$169.1546	$169.15	$169.15	$169.20
Purchase #5	$42.65	9.863%	$46.8566	$46.86	$46.85	$46.90
Purchase #6	$178.67	3.226%	$184.4339	$184.43	$184.45	$184.40
Purchase #7	$99.95	11.111%	$111.0554	$111.06	$111.05	$111.10
7 purchase totals =	$784.71		$844.9025	$844.90	$844.90	$845.00