We demonstrate a digital phase conjugation technique for generating a sharp focus point at the end of a multimode optical fiber. A sharp focus is experimentally obtained at the distal end of a 200 mu m core multimode fiber. By recording the digital holograms for different excitation conditions, the sharp focus can be digitally scanned over a 175 mu m diameter regular grid. The demonstrated technique is used for high resolution scanning lensless imaging based on multimode fibers, of stained biological samples that can enable diagnosis from the investigation of cellular phenotype.