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	$151.34	11.373%	$168.5519	$168.55	$168.55	$168.60
Purchase #2	$52.90	8.553%	$57.4245	$57.42	$57.40	$57.40
Purchase #3	$31.27	5.602%	$33.0217	$33.02	$33.00	$33.00
Purchase #4	$166.92	3.564%	$172.869	$172.87	$172.85	$172.90
Purchase #5	$135.85	6.315%	$144.4289	$144.43	$144.45	$144.40
Purchase #6	$62.98	4.836%	$66.0257	$66.03	$66.05	$66.00
Purchase #7	$111.75	7.624%	$120.2698	$120.27	$120.25	$120.30
7 purchase totals =	$713.01		$762.5915	$762.59	$762.55	$762.60