While we can't offer tax advice, our perspective is that the combined amount would be considered tax deductible. In the same way that if you were to donate to an organization and decide not to cover the fees, your full gift would be tax deductible. Since we've automatically calculated the fees into the gift, you essentially give the organization a specific amount that will be only used for covering fees.
RebelGive does not provide tax advice. Please consult your local tax professional about what portion of the full gift amount can be claimed as a charitable contribution.