Plant Identification Help

So, I bought what I thought was peppermint. After I'd planted and admired it for a few days, however, I noticed it looked a lot different than its tag:


It smells minty. It tastes kind of grassy, but kind of minty too, with a definite 'cooling' sensation in my mouth. The tag looks more like this peppermint:



Light green, bigger leaves, more upright plant.


I think it was, perhaps, mislabled. My actual plant is darker green, smaller, denser leaves, and seems to be spreading rather than growing up:







Ack! I planted it in my 'edible' garden full of herbs and edible flowers. I don't want anything in that garden that is inedible. I looked online, and it seems there are more varieties of mint/peppermint than I thought. For instance, this picture looks a lot more like my mystery plant:


It is described simply as peppermint. Which is encouraging, but notice, again, the upward growth. So maybe it's a variety of mint? I thought maybe Chocolate Mint, a cultivar of mint, and it does look similar, except there is no darker discoloration in the middle like this plant:


And while the stems are very green, there are stems that resemble the chocolate mint in this way (also, chocolate mint is a spreading ground cover):


Can anyone help me identify my plant? Or should I take it to a master gardener or something? Where should I take it? I'm serious about everything in this box of the garden being edible...I've even planted edible flowers.