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	$116.52	8.550%	$126.4825	$126.48	$126.50	$126.50
Purchase #2	$154.89	7.506%	$166.516	$166.52	$166.50	$166.50
Purchase #3	$214.49	3.509%	$222.0165	$222.02	$222.00	$222.00
Purchase #4	$49.38	11.863%	$55.2379	$55.24	$55.25	$55.20
Purchase #5	$132.78	10.852%	$147.1893	$147.19	$147.20	$147.20
Purchase #6	$97.72	13.679%	$111.0871	$111.09	$111.10	$111.10
Purchase #7	$146.89	5.405%	$154.8294	$154.83	$154.85	$154.80
7 purchase totals =	$912.67		$983.3587	$983.37	$983.40	$983.30