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	$57.85	10.243%	$63.7756	$63.78	$63.80	$63.80
Purchase #2	$6.57	9.541%	$7.1968	$7.20	$7.20	$7.20
Purchase #3	$155.43	11.407%	$173.1599	$173.16	$173.15	$173.20
Purchase #4	$92.38	5.365%	$97.3362	$97.34	$97.35	$97.30
Purchase #5	$150.59	13.656%	$171.1546	$171.15	$171.15	$171.20
Purchase #6	$95.25	5.628%	$100.6107	$100.61	$100.60	$100.60
Purchase #7	$61.35	6.384%	$65.2666	$65.27	$65.25	$65.30
7 purchase totals =	$619.42		$678.5004	$678.51	$678.50	$678.60