This is the same question I have. Memory usage is notoriously tricky to measure because of shared libraries and the like. So a simple figure like 95% doesn't end up meaning much at the end of the day. chrome://memory may be a good place to start.

Ninja edit: note the disclaimer at the bottom of chrome://memory:

    (Note: Due to memory sharing between processes, 
    summing memory usage does not give total memory usage.)