I based my attire on where the dinner was being held. Usually went no tie but one interview had the pre dinner at a pretty fancy place so I put on a tie. Some of the applicants had ties and others didn't; I don't think anyone cared.
I would wear business casual attire: khakis, chinos, corduroys, sweaters, button-downs, sport coats, nice shoes, etc. Do not wear sneakers or a t-shirt to these events unless you are interviewing in California.