I've searched for the all over the internet and have not been able to find anything. So I am trying to create some isometric art. Upon creating the boxes I noticed that if you zoom in as far as Inkscape will zoom - I think it's something like 25,900% - I can see that on some corners of the box the strokes are overlapping each other, and, the thing is, I had a set of isometric buildings rejected with a certain website where you can submit you artwork and I think it might have had something to do with this. Any ideas how to fix it? Image in question is attached.

Hi.

The depicted corner is the result of the stroke joins set to miter.
If you set rounded corners, there won't be any 'spikes".
Although I'm not sure if this could be the reason for any rejection. Maybe ask them about it.

Try looking at the bottom of this page
http://tavmjong.free.fr/INKSCAPE/MANUAL.html