How to align gridlines of primary and secondary verticak axis ?

Hello,

I have chart, that shows on horizontal axis customers and for them on primary vertical axis turnover and on secondary vertical axis customer's cost share on his turnover....

Everything is fine, only thing is that I want to keep gridlines in my chart, but with Interval AUTO I have always different number of major tick marks on primary and secondary axis and gridlines are not aligned, which looks nasty. Turning off gridlines for one of the axis is not solution

thanks for help