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	$14.56	8.105%	$15.7401	$15.74	$15.75	$15.70
Purchase #2	$18.93	4.634%	$19.8072	$19.81	$19.80	$19.80
Purchase #3	$53.48	3.504%	$55.3539	$55.35	$55.35	$55.40
Purchase #4	$18.65	11.640%	$20.8209	$20.82	$20.80	$20.80
Purchase #5	$13.28	3.382%	$13.7291	$13.73	$13.75	$13.70
Purchase #6	$51.31	12.285%	$57.6134	$57.61	$57.60	$57.60
Purchase #7	$35.29	13.123%	$39.9211	$39.92	$39.90	$39.90
7 purchase totals =	$205.50		$222.9857	$222.98	$222.95	$222.90