Varies quite a bit....we leave $2 or $3 per day for just DH & I. If they did a good job through the week, I'll leave a $5 on the day we check out...if it was a super job, $10 on last day. If more than 2 in the room, $1 per person per day is common, so family of 4 would tip $4 per day.
Some people just leave the same amount every day, regardless of number in the room...some leave the whole tip on the day they check out.