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	$131.75	7.389%	$141.485	$141.49	$141.50	$141.50
Purchase #2	$108.59	9.813%	$119.2459	$119.25	$119.25	$119.20
Purchase #3	$233.72	12.427%	$262.7644	$262.76	$262.75	$262.80
Purchase #4	$75.81	12.791%	$85.5069	$85.51	$85.50	$85.50
Purchase #5	$198.89	9.515%	$217.8144	$217.81	$217.80	$217.80
Purchase #6	$102.79	5.664%	$108.612	$108.61	$108.60	$108.60
Purchase #7	$38.25	6.653%	$40.7948	$40.79	$40.80	$40.80
7 purchase totals =	$889.80		$976.2234	$976.22	$976.20	$976.20