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	$192.32	10.281%	$212.0924	$212.09	$212.10	$212.10
Purchase #2	$129.92	8.799%	$141.3517	$141.35	$141.35	$141.40
Purchase #3	$94.86	3.109%	$97.8092	$97.81	$97.80	$97.80
Purchase #4	$205.37	5.248%	$216.1478	$216.15	$216.15	$216.10
Purchase #5	$99.94	11.659%	$111.592	$111.59	$111.60	$111.60
Purchase #6	$19.43	8.849%	$21.1494	$21.15	$21.15	$21.10
Purchase #7	$126.60	13.337%	$143.4846	$143.48	$143.50	$143.50
7 purchase totals =	$868.44		$943.6271	$943.62	$943.65	$943.60