Thank you. I hope yours is pleasant as well. I don't like either of your two choices, but if forced to choose I would say "likewise". "You too" doesn't make sense. You too WHAT? "Same to you" would make more sense. "Thank you" with a smile is sufficient.

Hi Sasha, both responses are acceptable; however, "Likewise" can seem a bit dismissive in connotation. It's a somewhat lazy response, one that the speaker uses because he/she feels the need to at least say something. "You too" is less general and generic, and indicates that you wish the person the exact same, to have a good day. Now, of course, this is not always true. A lot of times the speaker is not being dismissive. But "You too" is better.

You too is better. Can’t imagine saying likewise. Could also say “and you”.