After reading the above, I searched Google for "ATM Fees Spain." This is one of the information filled sites I came up with. It explains a lot.
Travelling to Spain and need cash? Our guide to ATMs in Spain, will help you locate them, explain fees, exchange rates, withdrawal limits and more.
transferwise.com
This dialog was also helpful...
A web search for ATM fees in Spain gets lots of hits, but the vast majority provide two inconsistent false claims. One is that the fee is charged by my (US) bank, not by the bank that owns the ATM...
travel.stackexchange.com
Also, if you Google "ATM fees Spain," scroll down to the "People Also Ask" section. Click on "What bank has the cheapest ATM fees?" That was also useful.
In the end, you need to do your own research. Also, I have some recommendations for you:
1. ONLY & EVER use an ATM connected to a real bank office that is not closed for good. This way, if the ATM eats your card, you can get it back.
2. NEVER use a free-standing ATM in a cafe / bar, gas station, tienda, train station, etc. UNLESS it is clearly the property of a major bank: Santander, BBVA, Banco Popular, etc. Check the artwork on the "box." You can actually buy an ATM device, load it with money, charge any amount you want to use it, and dispense cash. Many independent business types do this, and charge exorbitant fees.
3. Carry TWO cards that can be used as a debit cards. Make sure each has a FOUR DIGIT PIN number. Only these will work in Spain. This way, if one card goes awry, the other is a backup.
4.
When you do take money from an ATM, take enough for the next 3 - 4 days on Camino. There will be another ATM down the path...
Hope this helps.