If this were 5 cartons there might be an issue as a tax would probably be owed, but 5 packs is not much (unless this is a difference in terminology used in the US and EU). The x-ray machine will see the cigarettes but more than likely nothing will be said as it's not an issue.

If something were to require your bag to be opened in front of your parents you could always claim they were for a friend that asked you to bring some back because they're so cheap, but yeah you shouldn't smoke. It's bad for you and expensive.

Enjoy you flights and Poland.