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	$98.83	12.845%	$111.5247	$111.52	$111.50	$111.50
Purchase #2	$153.57	6.403%	$163.4031	$163.40	$163.40	$163.40
Purchase #3	$210.78	5.750%	$222.8999	$222.90	$222.90	$222.90
Purchase #4	$122.31	12.724%	$137.8727	$137.87	$137.85	$137.90
Purchase #5	$233.29	5.266%	$245.5751	$245.58	$245.60	$245.60
Purchase #6	$130.78	5.224%	$137.6119	$137.61	$137.60	$137.60
Purchase #7	$185.35	7.770%	$199.7517	$199.75	$199.75	$199.80
7 purchase totals =	$1,134.91		$1,218.6391	$1,218.63	$1,218.60	$1,218.70