I am Jenn And I am not smarter then a 4th grader!

OK 4th grade math problem. I have a potential answer of ten but the 4th graders are insisting the answer is 20 games or 4 rounds.

Five teams are competing in a tournament. Each team must
compete against each of the other teams once. How many
rounds of competition are needed.

What say yeeeeeeeeeeeeeeeeeeeehaw? I will post my work in the comment section after a few of you all offer me your two cents.