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	$127.82	3.182%	$131.8872	$131.89	$131.90	$131.90
Purchase #2	$6.53	4.563%	$6.828	$6.83	$6.85	$6.80
Purchase #3	$10.72	11.770%	$11.9817	$11.98	$12.00	$12.00
Purchase #4	$27.93	5.635%	$29.5039	$29.50	$29.50	$29.50
Purchase #5	$30.33	8.236%	$32.828	$32.83	$32.85	$32.80
Purchase #6	$84.58	7.168%	$90.6427	$90.64	$90.65	$90.60
Purchase #7	$21.50	11.636%	$24.0017	$24.00	$24.00	$24.00
7 purchase totals =	$309.41		$327.6732	$327.67	$327.75	$327.60