Actually, the possibility of a leak might be a bigger risk than any
fire hazard.

Your neighbor doesn't know how leak proof your containers are. You
might be able to prove it to him.

But think about it. If he has a well, and you drip a little gasoline
into the groundwater, he just lost his water supply.

Even if no well, if you contaminate the groundwater under his
property, he can no longer sell his house. You're probably liable for
his property loss as well as an environmental cleanup.

And if you're storing your gasoline perfectly, but the guy before you
dripped gasoline into the groundwater, you may have trouble proving it
wasn't you.

Of course that's true if you keep your gas cans in the shed too. But
your neighbor won't know.