Ask HN: Dressing Up for a Job Interview?

I haven't interviewed in about 10 years (IIRC).

I have an interview with a bank for a developer position. It's 2 hours both personal and technical interview combined.

I don't own a pair of slacks or a tie. I can go buy clothes to wear but is this really required now-a-days?

Can I just go in a "dressier" pair of jeans and a button down or sweater?

Or is the interview process still a dress up event?