Agricultural Business Security Tax Credit Act of 2005 - Amends the Internal Revenue Code to allow a retailer of agricultural products or a manufacturer, formulator, or distributor of certain pesticides a business tax credit for up to 50 percent of the cost of protecting certain hazardous chemicals or pesticides from unauthorized access. Sets an annual limit on such credit of $2 million and a per facility limitation of $100,000 (reduced by credits received for the five prior taxable years).