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	$22.79	6.717%	$24.3208	$24.32	$24.30	$24.30
Purchase #2	$52.75	4.144%	$54.936	$54.94	$54.95	$54.90
Purchase #3	$143.75	7.485%	$154.5097	$154.51	$154.50	$154.50
Purchase #4	$214.29	11.291%	$238.4855	$238.49	$238.50	$238.50
Purchase #5	$143.93	6.126%	$152.7472	$152.75	$152.75	$152.70
Purchase #6	$75.49	4.460%	$78.8569	$78.86	$78.85	$78.90
Purchase #7	$246.56	4.698%	$258.1434	$258.14	$258.15	$258.10
7 purchase totals =	$899.56		$961.9995	$962.01	$962.00	$961.90