If it's a couple, then every couple is different.
Some couples split everything 50-50 regardless of earnings, some put everything in one account and pay the bills and split the rest, some couples still have one person holding all the money, paying all the bills and giving 'pocket' money to the other (I could name names on that one!).
I wouldn't get hung up on exact amounts. My wife earns less than me, so although we put roughly half in each for shopping we each pay for our own petrol and clothes, and I pay a lot more of the mortgage than her to ensure she's not skint. Then for other things like electricity I tend to pay it, but if she's in town she will.
I can tell you from experience that if you go down the route of 'you owe a fiver more to make up your 55%' then you will end up arguing at least once a month.