There was a time when I tipped not much at all. Last time I was at CBR, tipped most days at $20. I have heard complaints about rooms and housekeeping, and I think that this happens because of a number of factors but slobby behavior could be a factor.
After paying $300 or more a day for the room, $20 seems reasonable. If I were going to leave $5 I probably wouldn't bother at all because of the insult factor.