(from Ruge Rules)
The rule: Place a comma before "or" when what follows it means the same as what precedes it.
As in: Please pass the salt, or sodium chloride.
But: Please pass the salt or pepper.
If "or" connects a long series of different items, the above rule is sometimes disregarded.
As in: He said he would accept payment in cash, or pledges, or goods, or services, or, even, promises of political support.
It's more correct as follows: He said he would accept payment in cash or pledges or goods or services, or, even, promises of political support.
You might also use commas in place of all but the last "or."