jpgraph如何设置y轴刻度随之增加

I want define a y-axis with a configured numbers since 30 to 100 as example 30 35 40 45 ... 95, 100. I set a scale:

$graph->SetScale("intint",30,100);

The result is 30 40 50 60 70 80 90 100 but I want a increase of 5.

I guess that's done via AxisPrototype::SetTextTickInterval($aStep, $aStart).