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	$128.71	11.562%	$143.5915	$143.59	$143.60	$143.60
Purchase #2	$68.29	5.484%	$72.035	$72.04	$72.05	$72.00
Purchase #3	$44.72	8.806%	$48.658	$48.66	$48.65	$48.70
Purchase #4	$9.74	12.481%	$10.9556	$10.96	$10.95	$11.00
Purchase #5	$180.69	5.521%	$190.6659	$190.67	$190.65	$190.70
Purchase #6	$169.29	13.762%	$192.5877	$192.59	$192.60	$192.60
Purchase #7	$248.39	4.103%	$258.5814	$258.58	$258.60	$258.60
7 purchase totals =	$849.83		$917.0751	$917.09	$917.10	$917.20