Marin County Parks will ask voters in November to renew a quarter-cent sales tax that supports parks, open space and agricultural lands countywide. Parks director Max Korten said extending the tax past its 2021 expiration date is critical for his department to continue the bulk of its work; the tax has generated over $82 million since two-thirds of voters approved it in 2012. “If we didn’t have Measure A, we would have to make a…