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	$158.83	7.546%	$170.8153	$170.82	$170.80	$170.80
Purchase #2	$48.57	9.823%	$53.341	$53.34	$53.35	$53.30
Purchase #3	$151.50	11.717%	$169.2513	$169.25	$169.25	$169.30
Purchase #4	$118.45	3.605%	$122.7201	$122.72	$122.70	$122.70
Purchase #5	$56.29	5.622%	$59.4546	$59.45	$59.45	$59.50
Purchase #6	$90.30	12.462%	$101.5532	$101.55	$101.55	$101.60
Purchase #7	$25.80	10.419%	$28.4881	$28.49	$28.50	$28.50
7 purchase totals =	$649.74		$705.6236	$705.62	$705.60	$705.70