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	$111.93	10.384%	$123.5528	$123.55	$123.55	$123.60
Purchase #2	$225.81	10.744%	$250.071	$250.07	$250.05	$250.10
Purchase #3	$112.47	12.847%	$126.919	$126.92	$126.90	$126.90
Purchase #4	$118.61	5.864%	$125.5653	$125.57	$125.55	$125.60
Purchase #5	$58.42	12.330%	$65.6232	$65.62	$65.60	$65.60
Purchase #6	$217.61	3.238%	$224.6562	$224.66	$224.65	$224.70
Purchase #7	$241.86	13.262%	$273.9355	$273.94	$273.95	$273.90
7 purchase totals =	$1,086.71		$1,190.3230	$1,190.33	$1,190.25	$1,190.40