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	$10.94	4.802%	$11.4653	$11.47	$11.45	$11.50
Purchase #2	$243.41	3.487%	$251.8977	$251.90	$251.90	$251.90
Purchase #3	$13.47	10.106%	$14.8313	$14.83	$14.85	$14.80
Purchase #4	$210.67	8.506%	$228.5896	$228.59	$228.60	$228.60
Purchase #5	$241.54	13.820%	$274.9208	$274.92	$274.90	$274.90
Purchase #6	$88.45	8.462%	$95.9346	$95.93	$95.95	$95.90
Purchase #7	$60.53	3.431%	$62.6068	$62.61	$62.60	$62.60
7 purchase totals =	$869.01		$940.2461	$940.25	$940.25	$940.20