The best way to handle this issue, is to realize that most cashiers at stores are often as nervous about other customers as you are about them. With that shared fear, it's good to lighten the mood, by saying something along the lines of, "Hello, Are you having a good day," or "Hey there, How are you," to show that you aren't just there to awkwardly transaction money, but to spread the joy of life you have within you with them as you go along your day. Just asking them about their day, does wonders for a lot of people, for most cashiers do not get to enjoy these kinds of conversations due to the oftentimes professional atmosphere cashiers have to project(and sometimes even get fired for if they do not), and if they do, they're quite awkward as the other person often trails off or doesn't add to the conversation and is more focused on paying for the thing they're buying instead of the cashier him/herself. This kind of exchange can be troublesome for some cashiers, because it's very impersonal when either awkwardly staring at them with little to say, or when they say hi, and the cashier thinks that they are hoping to have a small conversation, yet, they don't continue it after they respond, because they think the cashier should continue the conversation more than they have. That is the very problem many people have with conversations these days, there is little actual exchanges in conversations (give and take). It's only a receiving expectation for many people in conversations these days, and it is an unfortunate affair that taking initiative in converations has gone by the wayside. Giving in a conversation is just as important if not more than receiving, in most situations. Being aware of all of this going on, is just one of many different things, that would eclipse your previous fears of cashiers.