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	$111.27	7.752%	$119.8957	$119.90	$119.90	$119.90
Purchase #2	$43.98	13.498%	$49.9164	$49.92	$49.90	$49.90
Purchase #3	$212.94	5.838%	$225.3714	$225.37	$225.35	$225.40
Purchase #4	$44.67	13.523%	$50.7107	$50.71	$50.70	$50.70
Purchase #5	$66.25	6.579%	$70.6086	$70.61	$70.60	$70.60
Purchase #6	$49.89	3.803%	$51.7873	$51.79	$51.80	$51.80
Purchase #7	$28.71	13.431%	$32.566	$32.57	$32.55	$32.60
7 purchase totals =	$557.71		$600.8561	$600.87	$600.80	$600.90