Open bar etiquette at weddings

Small wedding at a restaurant, it’s open bar until their tab runs out then cash bar. I have horrible anxiety and I’m definitely one of those “2-3 drinks just to feel like a normal person” type of girl 😂 so I was curious if it’s a thing to offer to pay cash for drinks so it doesn’t decimate their open bar tab if I end up getting multiple drinks? Or will that just be annoying and confusing for the bartender? Probably lol