This can be done by collecting all the emails into a single field and using our variables and calculation system, and then using that field to fill the email response recipients line in the "email question" drop-down of the autoresponder.
Each email would be set as a variable in a calculated field (named "email1", "email2", etc.) and then calculated into the hidden field with a formula that separates each value by a comma. (email1 + "," + "email2" + ","....)
You'll then use that field in in the section of your notifications tab that said "Email Question" that will trigger where to send your autoresponses. For it to be listed in this drop down, the field will have to validated as an email address in your form builder.