When someone says that they don't have two nickels to rub together it's basically just meaning that the person is poor and has no money or not much money at all.
Some people may say that they didn't have two nickels to rub together when they were once poor or they may still be poor financially.
The don't have two nickels to rub together is an old saying that just means that you're broke and poor.
Although even if you did have two nickels now to rub together you would still be considered poor because you cannot buy much today with two nickels which is only 10 cents.
Even 1 dollar or 2 dollars won't buy much of anything today.