Swords enchanted with Sharpness do not deal more damage to the Ender Dragon. However, the bow enchantment Power does inflict more damage.
Steps to Reproduce:
1. Make a new Creative World.
2. Construct an End Portal and enter it.
3. Get two diamond swords from the creative inventory.
4. Enchant one sword with Sharpness V using an Anvil and an enchanted book. Leave the other one un-enchanted.
5. Hit the Ender Dragon with both and notice the same amount of damage is dealt.
Confirmed the Sharpness part as Knockback and Fire Aspect not working on the dragon is intended. Changed summary accordingly.