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	$100.51	10.813%	$111.3781	$111.38	$111.40	$111.40
Purchase #2	$110.51	8.394%	$119.7862	$119.79	$119.80	$119.80
Purchase #3	$96.36	9.417%	$105.4342	$105.43	$105.45	$105.40
Purchase #4	$150.59	5.396%	$158.7158	$158.72	$158.70	$158.70
Purchase #5	$43.52	4.811%	$45.6137	$45.61	$45.60	$45.60
Purchase #6	$40.88	3.243%	$42.2057	$42.21	$42.20	$42.20
Purchase #7	$122.80	10.768%	$136.0231	$136.02	$136.00	$136.00
7 purchase totals =	$665.17		$719.1568	$719.16	$719.15	$719.10