dojo stop dropdown button from closing on checkbox select

Question

here is the html:

<button data-dojo-attach-point="pinFilterButton" data-dojo-type="dijit/form/DropDownButton">
    <span>Proj. PIN</span>
    <select multiple="true" name="multiselect" data-dojo-attach-point="pinFilter" data-dojo-type="dojox.form.CheckedMultiSelect"></select>
</button>

I just want to stop the dropdown from closing when a checkbox is selected.

Here is what I tried:

on(t.pinFilterButton.dropDownContainer, 'close', function (e) {
    e.stopPropogation();
})

among other variations.