Flickering between edges of cuboids right next to each other.

I am making a game engine, and to make the game world, I decided to use cuboid geometry. I have cube vertices in a VBO, and I also use an IBO for it as well. Whenever I place 2 cuboid objects right next to each other on the same plane, I can see these flickering pixels between the two. I found out that these pixels are actually little holes, and I can see the background color through them. How can I prevent this? Thanks!

Heres a picture:

In the picture, I have 3 world geometry objects next to each other.

Looks like an aliasing artifact to me. Try making the cuboids exactly the same size. This would put vertices of neighboring cuboids exactly on top of each other. In the figure, it looks like the middle cuboid is larger.