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	$92.59	13.815%	$105.3813	$105.38	$105.40	$105.40
Purchase #2	$155.96	10.390%	$172.1642	$172.16	$172.15	$172.20
Purchase #3	$230.49	11.786%	$257.6556	$257.66	$257.65	$257.70
Purchase #4	$85.94	7.130%	$92.0675	$92.07	$92.05	$92.10
Purchase #5	$132.38	3.108%	$136.4944	$136.49	$136.50	$136.50
Purchase #6	$10.56	4.757%	$11.0623	$11.06	$11.05	$11.10
Purchase #7	$217.73	9.509%	$238.4339	$238.43	$238.45	$238.40
7 purchase totals =	$925.65		$1,013.2592	$1,013.25	$1,013.25	$1,013.40