Basically, if no other condition is given, then, tossing two coins five times is just same as tossing a coin ten times.
First of all, we need to choose 5 positions out of 10 which will have 5 heads. We can do this in 10C5 ways. The remaining 5 positions will be chosen automatically for the 5 tails.
As the probability of getting a head or a tail is 0.5, the probability of getting 5 heads and 5 tails will be (10C5)(0.5^5)(0.5^5) which will be approximately 0.246.