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	$116.89	13.330%	$132.4714	$132.47	$132.45	$132.50
Purchase #2	$111.44	4.577%	$116.5406	$116.54	$116.55	$116.50
Purchase #3	$190.86	13.263%	$216.1738	$216.17	$216.15	$216.20
Purchase #4	$207.45	6.799%	$221.5545	$221.55	$221.55	$221.60
Purchase #5	$57.78	8.375%	$62.6191	$62.62	$62.60	$62.60
Purchase #6	$71.82	6.473%	$76.4689	$76.47	$76.45	$76.50
Purchase #7	$5.25	3.833%	$5.4512	$5.45	$5.45	$5.50
7 purchase totals =	$761.49		$831.2795	$831.27	$831.20	$831.40