When you add an axis, there are several options you can use for the tick marks. Example:
chart.addAxis("y", {
majorTicks : true, // default
majorLabels : true, // default
majorTick : {length: 4, color: "#FFF"},
majorTickStep : 10,
minorTicks : true,
minorLabels : true,
minorTick : { length: 2, color: "#CCC"},
minorTickStep : 5,
...
vertical: true
});
Check the API docs for more: http://dojotoolkit.org/api/1.8/dojox/charting/axis2d/Default