You'd have to flatten the matrix into a 1d vector, sort that, then reshape it back to the initial shape. See https://in.mathworks.com/help/matlab/ref/reshape.html for how to reshape an array, and https://in.mathworks.com/help/matlab/ref/sort.html for how to sort. The code would be something like:
a = reshape(A, [250,1])
a = sort(a)
A = reshape(a, [5,5,10])
