Only works if you KNOW your going to die/kill yourself to get back to your spawn point. 
Step 1. Select a coin you currently have on you. (e.g. you have 3 gold coins on you. Select those, but keep the on your cursor!) 
step 2. Murder yourself. My favorite is to jump in lava, and go out like a T-850 
step 3. upon coming back from your trip to hell and back, place the coin that is still on your cursor back in your inventory.  
 
You have lost some coins, but not those trusty Gold or Sliver coins you hold so dearly.  

I keep my money in a chest/piggy bank. If you save & quit, then reload the game, you'll be back at your spawn anyways, so just do that if you think you're going to die.

That's a good idea. Also, when my inventory is full I select an item and keep it on my cursor which frees up 1 extra space, then just walk back to your chests and place the item you were holding.