But, there's a few things you can do to make it a little easier. A fewThese are some I found from my experiences.
This one is maybe counter-intuitive, and other trans/GNC people might have different opinions here. It also mostly applies to visibly nervous people. But, let the personcustomer talk to you if they need something. Don't go up to them to ask if you can help find anything, or anything like that. And, somewhat obviously, don't watch them as they are shopping.
If you are required to talk to customers, then try to do so in a way that the customer can be non-committal and easily back out of the conversation. You can probably get away with "Anything I can help you find?", which lets the customer respond with "Just looking around" pretty easily. Or, I liked Juliana's suggested wording, "Hi, I'm Nicki. If there is anything I can help you with, I'll be by the counter." The goal here is to keep the onus of conversation off the customer, because social anxiety, on top of everything else, is a lot to deal with.
When I was first shopping, it would mostly be around 3 am at Walmart, so I could avoid anyone seeing me and then use the self checkouts. When I got a little bolder and started looking in the daylight, I was always terrified of people coming up to me an offering to help - even in good faith! It's just scary to have to respond when you're doing something that feels like a taboo, even if you know you're doing nothing wrong. Most of the time, after someone asked, I would just leave, because it made me too nervous. There's a lot more at play here than just my trans status, to be fair, but just the same, it would have been much easier to never have anyone talk to me.
Ultimately, you will notice that there weren't a lot of strictly individual interpersonal skills here. Most of what I've described requires the store itself to be on board, and to make broader changes than 1 individual interaction. That's required, unfortunately - transphobia (which applies here regardless of whether the personcustomer is actually trans), is a systemic issue, and requires more than just individual action to fight. Making inclusive spaces is not just about not rejecting people, but finding ways to be actively accepting, which is definitely more complex.