I think I figured this out. I tried everything and the cookies kept reappearing. Sometimes almost instantly. I finally realized it is because my iPhone and iPad kept synching with my MacBook Pro.
When I deleted cookies on my MacBook, I had no idea they were being reinstalled by auto-synching the other devices (that were in different places around my house).
After I deleted cookies in all three devices, nothing has reappeared in the last few hours.