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	$93.32	4.182%	$97.2226	$97.22	$97.20	$97.20
Purchase #2	$97.70	13.716%	$111.1005	$111.10	$111.10	$111.10
Purchase #3	$113.46	3.127%	$117.0079	$117.01	$117.00	$117.00
Purchase #4	$89.43	11.856%	$100.0328	$100.03	$100.05	$100.00
Purchase #5	$121.77	7.484%	$130.8833	$130.88	$130.90	$130.90
Purchase #6	$95.32	9.580%	$104.4517	$104.45	$104.45	$104.50
Purchase #7	$11.33	7.478%	$12.1773	$12.18	$12.20	$12.20
7 purchase totals =	$622.33		$672.8761	$672.87	$672.90	$672.90