Donate % of profit at checkout

Hi there, I building a small e-commerce and want to setup an option where customers can choose to which NGO institution the brand donates a percentage of the proceeds to.

Something like at checkout, the customer chooses from a list of 5 institutions.

In this case, I believe the donation block doesn't work for because I don't want clients to pay extra for the donation, I just want them to select the institution of choice so the store can repass 5% of the profits to.

Any insight on how I can make this happen?

Thanks!