Set up the slider like this in your start up code (untested):
sliderMin = get(handles.slider, 'Min');
sliderMax = get(handles.slider, 'Max');
increment = 1/(sliderMax-sliderMin);
sliderStep = set(handles.slider, 'Step', [increment, 2*increment]);
To get the integer value later:
sliderValue = round(get(handles.slider, 'Value'));
