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	$64.74	4.179%	$67.4455	$67.45	$67.45	$67.40
Purchase #2	$203.48	4.664%	$212.9703	$212.97	$212.95	$213.00
Purchase #3	$158.40	10.575%	$175.1508	$175.15	$175.15	$175.20
Purchase #4	$50.28	13.651%	$57.1437	$57.14	$57.15	$57.10
Purchase #5	$83.91	3.283%	$86.6648	$86.66	$86.65	$86.70
Purchase #6	$90.35	11.235%	$100.5008	$100.50	$100.50	$100.50
Purchase #7	$34.32	3.434%	$35.4985	$35.50	$35.50	$35.50
7 purchase totals =	$685.48		$735.3744	$735.37	$735.35	$735.40