Either way, you'll have to explain yourself in the interview. Group dismissal is technically correct, but it's vague. If I saw that, I would question what it was. Were you laid off? Why was it a group dismissal? It leaves too many open-ended questions.
You can state termination for violating policy, which is technically correct since theft is against all employer's policy. Then in the interview, you can indicate that you and two others were terminated due to possible theft. You can say you did not steal anything, but you can't prove it either way. It's up to the interviewer to determine what is right and what isn't.