Would it be wrong of me to spend this tip a customer gave me?

I started working at McDonald's the other day. Right before my shift I was walking into the building and a husband and wife walked in and I held the door for them. We talked about rain, and had a pleasant conversation. Fast forward to last night i was running orders out to the parking lot, and one of the orders was for them. He asked if I remember them, and I said yes, then he gave me a $20 tip. I declined but I eventually accepted. Anyways. I just read its a serious violation eccepting tips. I was just maybe gonna not spend it in case the customer tells my boss that he tipped me, and I can give it to whomever I need to.

Would it be wrong of me to spend this tip a customer gave me?
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