Preserving Social Security Act of 2005 - Amends title II (Old Age, Survivors and Disability Insurance) (OASDI) of the Social Security Act with regard to the Federal Old-Age and Survivors Insurance Trust Fund and the Federal Disability Insurance Trust Fund to revise requirements for the issuance of obligations for purchase by the Funds. Establishes an effective annual rate of interest at 4.7 percent for such obligations.