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	$237.86	9.749%	$261.049	$261.05	$261.05	$261.00
Purchase #2	$137.61	4.534%	$143.8492	$143.85	$143.85	$143.80
Purchase #3	$136.39	8.816%	$148.4141	$148.41	$148.40	$148.40
Purchase #4	$82.50	9.251%	$90.1321	$90.13	$90.15	$90.10
Purchase #5	$39.66	13.633%	$45.0668	$45.07	$45.05	$45.10
Purchase #6	$238.81	7.158%	$255.904	$255.90	$255.90	$255.90
Purchase #7	$14.77	4.814%	$15.481	$15.48	$15.50	$15.50
7 purchase totals =	$887.60		$959.8962	$959.89	$959.90	$959.80