You should be able to fit 5 no problem. I edited my post to reduce the depth to 18 inches, since I measured again, and there does seem to be some variability in the depth (manufacturing tolerances, I guess).
GE 10.6-cu ft Chest Freezer (White) ENERGY STAR Model #: FCM11PHWW
For Posterity:
Floor:
34" wide
18" deep
25 1/4" height above*
Hump (right side):
9" wide
18" deep
16 1/2" height above
If you have the right ball lock kegs (exactly 8.5 inches in diameter, or slightly out of...