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	$143.81	11.680%	$160.607	$160.61	$160.60	$160.60
Purchase #2	$213.67	3.649%	$221.4668	$221.47	$221.45	$221.50
Purchase #3	$95.51	9.486%	$104.5701	$104.57	$104.55	$104.60
Purchase #4	$63.83	3.797%	$66.2536	$66.25	$66.25	$66.30
Purchase #5	$82.84	5.534%	$87.4244	$87.42	$87.40	$87.40
Purchase #6	$51.56	6.473%	$54.8975	$54.90	$54.90	$54.90
Purchase #7	$193.94	12.121%	$217.4475	$217.45	$217.45	$217.40
7 purchase totals =	$845.16		$912.6669	$912.67	$912.60	$912.70