I need to stumble across a few bucks, so that I'll have $5 in cash for Chinese take-out for Sunday lunch. Other than that, I have no need for cash for the duration of the weekend.
I have about 3000 euro but its all in an account I cant open from my present location. I should be getting some on my functional account any day now. I still have some food stored and i can steal from housemates.
Usually, $5. I switched over almost entirely to plastic (the $5 is just-in-case thing), because if I have cash on me, I spend it, and I spend it quickly. Don't even notice it.