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	$45.31	6.308%	$48.1682	$48.17	$48.15	$48.20
Purchase #2	$27.80	13.615%	$31.585	$31.59	$31.60	$31.60
Purchase #3	$241.57	12.427%	$271.5899	$271.59	$271.60	$271.60
Purchase #4	$34.70	8.592%	$37.6814	$37.68	$37.70	$37.70
Purchase #5	$47.25	7.759%	$50.9161	$50.92	$50.90	$50.90
Purchase #6	$131.81	5.673%	$139.2876	$139.29	$139.30	$139.30
Purchase #7	$136.34	10.616%	$150.8139	$150.81	$150.80	$150.80
7 purchase totals =	$664.78		$730.0421	$730.05	$730.05	$730.10