Pennyroyal oil is poisonous, but the amount of oil you'd get from using the herb in a wine is not going to hurt you unless you're pregnant. In which case, you shouldn't be drinking wine anyway.
Right from wikipedia: "Pennyroyal was commonly used as a cooking herb by the Greeks and Romans. The ancient Greeks often flavored their wine with pennyroyal. A large number of the recipes in the Roman cookbook of Apicius call for the use of pennyroyal, often along with such herbs as lovage, oregano and coriander. Although still commonly used for cooking in the Middle Ages, it gradually fell out of use as a culinary herb and is seldom used so today."
It's like saying alcohol is toxic (which it is), yet here we are making it with the intention of ingesting it. In small quantities. The amount you'd use for flavouring is like the cyanide in apple seeds...
I've had pennyroyal tea myself and it's pleasant, my mom used to grow it, and for a while was calling it "ratnip" because I had a pet rat that would go bugnutz for the fresh stuff. We also used the essential oil (very, very diluted, it IS toxic) as an ingredient in a flea spray for the dog.
"The main ingredient needed is 'time' followed closely by 'patience'." - The Bishop 2013
"Good grief! If someone wanted to murder you, all they would have to do is ship you a 55 gallon barrel of honey and watch you document working yourself to death!" - Vance G