But their lowest tier of VPS caps out at $5 a month

https://www.digitalocean.com/pricing/

I believe they meant you only need it for a couple hours max so with the hourly rate it'd only be less than $0.02

IIRC they have a minimum payment. You need to put $5 in your account. Not sure what they do if you pay by subscription and only use a few hours, but when I was using DO, you needed to fund your account with $5 even if you were using the $100 free credit from GitHub education.

This is the case for PayPal and Visa debits, but not credit cards IIRC.