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	$136.76	8.389%	$148.2328	$148.23	$148.25	$148.20
Purchase #2	$197.27	11.249%	$219.4609	$219.46	$219.45	$219.50
Purchase #3	$182.45	5.743%	$192.9281	$192.93	$192.95	$192.90
Purchase #4	$56.43	12.643%	$63.5644	$63.56	$63.55	$63.60
Purchase #5	$177.83	10.153%	$195.8851	$195.89	$195.90	$195.90
Purchase #6	$204.32	8.430%	$221.5442	$221.54	$221.55	$221.50
Purchase #7	$37.91	7.756%	$40.8503	$40.85	$40.85	$40.90
7 purchase totals =	$992.97		$1,082.4658	$1,082.46	$1,082.50	$1,082.50