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	$93.92	11.292%	$104.5254	$104.53	$104.55	$104.50
Purchase #2	$192.61	6.434%	$205.0025	$205.00	$205.00	$205.00
Purchase #3	$34.79	10.725%	$38.5212	$38.52	$38.50	$38.50
Purchase #4	$42.89	6.605%	$45.7229	$45.72	$45.70	$45.70
Purchase #5	$156.29	10.382%	$172.516	$172.52	$172.50	$172.50
Purchase #6	$92.31	8.514%	$100.1693	$100.17	$100.15	$100.20
Purchase #7	$28.25	5.579%	$29.8261	$29.83	$29.85	$29.80
7 purchase totals =	$641.06		$696.2834	$696.29	$696.25	$696.20