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	$226.32	12.686%	$255.031	$255.03	$255.05	$255.00
Purchase #2	$171.98	11.822%	$192.3115	$192.31	$192.30	$192.30
Purchase #3	$246.48	3.494%	$255.092	$255.09	$255.10	$255.10
Purchase #4	$219.74	12.284%	$246.7329	$246.73	$246.75	$246.70
Purchase #5	$12.71	9.585%	$13.9283	$13.93	$13.95	$13.90
Purchase #6	$63.58	9.312%	$69.5006	$69.50	$69.50	$69.50
Purchase #7	$48.88	7.594%	$52.5919	$52.59	$52.60	$52.60
7 purchase totals =	$989.69		$1,085.1882	$1,085.18	$1,085.25	$1,085.10