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	$55.95	10.853%	$62.0223	$62.02	$62.00	$62.00
Purchase #2	$61.95	11.854%	$69.2936	$69.29	$69.30	$69.30
Purchase #3	$36.57	5.286%	$38.5031	$38.50	$38.50	$38.50
Purchase #4	$31.71	12.144%	$35.5609	$35.56	$35.55	$35.60
Purchase #5	$35.53	12.780%	$40.0707	$40.07	$40.05	$40.10
Purchase #6	$50.63	3.227%	$52.2638	$52.26	$52.25	$52.30
Purchase #7	$196.70	4.463%	$205.4787	$205.48	$205.50	$205.50
7 purchase totals =	$469.04		$503.1931	$503.18	$503.15	$503.30