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	$14.37	6.192%	$15.2598	$15.26	$15.25	$15.30
Purchase #2	$90.69	13.670%	$103.0873	$103.09	$103.10	$103.10
Purchase #3	$217.67	6.523%	$231.8686	$231.87	$231.85	$231.90
Purchase #4	$10.27	5.334%	$10.8178	$10.82	$10.80	$10.80
Purchase #5	$132.55	9.230%	$144.7844	$144.78	$144.80	$144.80
Purchase #6	$82.90	8.160%	$89.6646	$89.66	$89.65	$89.70
Purchase #7	$143.52	7.668%	$154.5251	$154.53	$154.55	$154.50
7 purchase totals =	$691.97		$750.0076	$750.01	$750.00	$750.10