A method of stimulating tissue of a patient is provided. The method comprises placing an array of electrodes in proximity to the tissue, conveying electrical current between the electrodes of the array to stimulate a tissue site, incrementally shifting the electrical current from at least one cathode to at least another cathode over a first range of fractionalized current values, and incrementally shifting the electrical current from at least one anode to at least another anode over a second range of fractionalized current values. The step sizes for the first and second ranges of fractionalized current values differ.