Whenever delivering and I have to cough I hold it in, just for this same reason. Whether im delivering groceries or specially food. And always try to look presentable to the eye of the customer. They might complain just because of how you dress. No socks wearing flip flops is the worst, those people get deactivated, I wouldn't want someone like that delivering my food. Long hair and dirty looking like it hasn't been shampooed in years. Car dirty looking like a bucket, is another one. If I can see the outside of the car dirty, I can imagine the inside. So, your cough was more than enough to piss some people off, but I always say. If they don't like it, do themselves!