GLSL: Render into 5 components of the textures

I am using the rendering more for a calculation step, and my goal is to calculate 5 values at a time.

As I know I could render into a texture with RGB or RGBA values, so 3 or 4 values. For the moment I am 2 textures of RGB and render into both at a time, so for the moment I have one unused value.

My question is, if there is a way to manipulated the texture, so I can store 5 values into it.

For these 5 values is important to say, I should be able to read out of it and to write to it.