I don't think there is any card that offers flat 5% on all spending.
Some offer 5% - 6% on certain spending categories and/or seasonally.
The best flat cash back rate on any spending I know of is citi double cash at 2%.
I think that having up to 3 cards and using them for what they are best at you can get average 3.5% cashback the most. But then it is a lot of work to keep track which one to use when, at least for me.