I have high blood pressure and still do inversions. I feel a slight headache if I do too much but never really had any problems. My advice is just do what's comfortable and don't push it if you have HBP. It definitely does relieve stress to the point where i often fall asleep afterwards - I even sometimes nod out while inverted (though I wake up quickly as the blood keeps flowing to the head).
Also spending a minute to check your BP beforehand would be a wise precaution (that I just might follow myself now that I think of it).