The central bank said it had sold $37.6 million at a cut-off price of 7.1401 pounds on Monday, almost unchanged from the 7.1402-pound cut-off price at the previous sale on Thursday. It had offered $40 million.
The dollar was offered for 7.39 pounds in the black market on Monday, weaker than Thursday's rate of 7.37 pounds, a black market trader said.
The pound had strengthened in the black market after the election victory last month of former army chief Abdel Fattah al-Sisi, who was sworn in as president on Sunday.
Traders had predicted a temporary appreciation in the parallel market following the election, citing hopes of new investment and aid from Gulf Arab countries, which have already given billions in aid to help stave off an economic collapse.
The pound had traded at around 7.50 pounds to the dollar before the elections.
The rates at which banks are allowed to trade dollars are determined by the results of the central bank sales, giving the bank effective control over official exchange rates.