function main()
{
app.beginUndoGroup("Layer time fix (round frames)");

// Helper variables
var proj = app.project;
var comp = proj.activeItem;
var layers = comp.selectedLayers;
var frameRate = comp.frameRate;

for (var i = 0; i < layers.length; i++)
{
    layers[i].inPoint = (1/frameRate) * (Math.round(layers[i].inPoint / (1/frameRate)));
    layers[i].outPoint = (1/frameRate) * (Math.round(layers[i].outPoint / (1/frameRate)));
}

app.endUndoGroup();
}

main();