Commissions are always negotiable. Some agents believe a higher commission gets more sales. I believe they definitely get more showings. But as other posts have pointed out, NEVER try to set a standard !!!
A word of warning: there's nothing funny or to be taken lightly about agents discussing commissions in a public forum.
This has been discussed ad nauseum on this website as to why that is and I would suggest you brush up on anti-trust laws and why it is better to err on the side of caution regarding this issue.
It could save you a lot of grief.
All commissions are negotiable between you and your agent, there are no set standards as it would be against Federal Laws, in particular the Shearman Anti Trust Act, etc. --choose your agent with care.