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	$97.81	4.175%	$101.8936	$101.89	$101.90	$101.90
Purchase #2	$75.94	9.344%	$83.0358	$83.04	$83.05	$83.00
Purchase #3	$52.62	9.210%	$57.4663	$57.47	$57.45	$57.50
Purchase #4	$148.98	12.670%	$167.8558	$167.86	$167.85	$167.90
Purchase #5	$30.60	5.104%	$32.1618	$32.16	$32.15	$32.20
Purchase #6	$13.59	12.265%	$15.2568	$15.26	$15.25	$15.30
Purchase #7	$43.93	7.204%	$47.0947	$47.09	$47.10	$47.10
7 purchase totals =	$463.47		$504.7648	$504.77	$504.75	$504.90