I actually know a bit about tamoxifen because a lot of the guys I grew up with wound up using anabolic steroids. Tamoxifen was a drug they used during and after their steroid cycles to prevent excess estrogen (caused by aromatase) from giving them gynecomastia. From what I remember, none of them ever had any sort of problem from using tamoxifen. As a matter of fact, tamoxifen was always talked about as a relatively 'safe' drug compared to a lot of the other stuff they were messing with at the time.
As far as it being an antifungal, that's the first I've heard. I always thought it was used to lower estrogen levels in women with breast cancer.