It is already 0.05 here.
All it does is make a mockery of the law.
First of all, a police officer isn't going to test everyone. They are going to test A) those that show driving impairment (or smell like booze I suppose), and B) those that pass by those occasional checkpoints.
Two things are going to be the result, neither of them positive to the whole idea of DUI enforcement.
First more people are going to be breaking the law, and not being caught. This will cause people to not take it seriously. People will be over 0.05 all the time, while showing no impairment, and not being tested. Which will then start giving people the idea, who cares about the law. It's like driving 120kph on the 401 in Ontario, it is against the law, but no one pays any attention to it anymore, including the police.
Second, for those that do get caught, by passing though some sort of random check point crack down (even then you would have to look impaired), people will be incredulous about it "What do you mean I blew over, I only had two drinks! Do you really think I am impaired?" label it bullshit and write it off as simply a ludicrous law further eroding its legitimacy.
You are also going to have more people challenging the accuracy of the measurement devices, which there have been a lot of proven problems in the past.