What should a Server tip the bartender?

What percentage of a servers total sales or server bar sales should the server tip the bartender? What do they do where you work? The upscale restaurant I work at just changed the percentage from 7 1/2% of server bars sales down to 5%.. Why would the server ever get more than half of the tip on the drink they punched in and I made. It is about a 20 to 30% pay-cut for me and makes no sense. The majority of what I make are martinis, old fashions, blended drinks and wine. I'm not just opening cans of beer, I have to be good and damn quick. What happened was a greedy server complained she thought we were getting too much and somehow got her way. I asked her why she thought she deserved more than half the tip and she replied 5% was the national average. Sounds like a load of crap to me.. They forget the bar doesn't get the automatic 15 - 20% from its customers like the dinner tab will get with the same drinks I made on it. They now get 15% and I get 5% on a 20% tip. Crappy!