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	$216.77	3.151%	$223.6004	$223.60	$223.60	$223.60
Purchase #2	$46.57	11.427%	$51.8916	$51.89	$51.90	$51.90
Purchase #3	$208.80	6.701%	$222.7917	$222.79	$222.80	$222.80
Purchase #4	$9.77	9.185%	$10.6674	$10.67	$10.65	$10.70
Purchase #5	$76.69	13.211%	$86.8215	$86.82	$86.80	$86.80
Purchase #6	$69.43	5.311%	$73.1174	$73.12	$73.10	$73.10
Purchase #7	$9.56	11.512%	$10.6605	$10.66	$10.65	$10.70
7 purchase totals =	$637.59		$679.5505	$679.55	$679.50	$679.60