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	$208.90	6.379%	$222.2257	$222.23	$222.25	$222.20
Purchase #2	$65.29	11.538%	$72.8232	$72.82	$72.80	$72.80
Purchase #3	$48.43	5.533%	$51.1096	$51.11	$51.10	$51.10
Purchase #4	$41.75	8.661%	$45.366	$45.37	$45.35	$45.40
Purchase #5	$111.45	9.259%	$121.7692	$121.77	$121.75	$121.80
Purchase #6	$34.34	6.594%	$36.6044	$36.60	$36.60	$36.60
Purchase #7	$185.77	13.718%	$211.2539	$211.25	$211.25	$211.30
7 purchase totals =	$695.93		$761.1520	$761.15	$761.10	$761.20