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	$215.46	3.243%	$222.4474	$222.45	$222.45	$222.40
Purchase #2	$88.60	10.317%	$97.7409	$97.74	$97.75	$97.70
Purchase #3	$40.29	13.595%	$45.7674	$45.77	$45.75	$45.80
Purchase #4	$138.94	10.467%	$153.4828	$153.48	$153.50	$153.50
Purchase #5	$87.95	13.401%	$99.7362	$99.74	$99.75	$99.70
Purchase #6	$47.57	13.587%	$54.0333	$54.03	$54.05	$54.00
Purchase #7	$62.71	4.758%	$65.6937	$65.69	$65.70	$65.70
7 purchase totals =	$681.52		$738.9017	$738.90	$738.95	$738.80