Ideally, instead of all being in the same row, there'd be five columns, with one picture in each cell.

But barring that, to me the easiest thing would be to change all the images from wrapping "in line with text" to "Square" or something else. Then you can select all the images in the row and use the Align tools to Distribute Horizontally.

That works for one row, but if you want row after row to also line up vertically, again, you'd be better off breaking your rows into columns so you have an even grid. You could do that and make the internal column borders non-printing.

Another possibility - if you have to leave them in line with text, add a wide white border around each image which should provide the same space left and right on each image. You'll also have that white space top and bottom as well.

When I inserted five pictures in one row, and resized them, the in line with text option seemed to automatically butt them up tightly against each other. I'm surprised yours didn't do that?