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	$100.70	4.772%	$105.5054	$105.51	$105.50	$105.50
Purchase #2	$114.34	5.667%	$120.8196	$120.82	$120.80	$120.80
Purchase #3	$10.84	13.691%	$12.3241	$12.32	$12.30	$12.30
Purchase #4	$36.56	12.158%	$41.005	$41.01	$41.00	$41.00
Purchase #5	$100.29	11.211%	$111.5335	$111.53	$111.55	$111.50
Purchase #6	$132.85	12.820%	$149.8814	$149.88	$149.90	$149.90
Purchase #7	$18.61	3.575%	$19.2753	$19.28	$19.30	$19.30
7 purchase totals =	$514.19		$560.3443	$560.35	$560.35	$560.30