EMLab P&K also tested refrigerator door handles and produce. It found similarly unpleasant results. Take a look at a complete breakdown of those findings here.
While the results aren't thrilling, the study is limited. It looked at just two stores in each category. Inside each store, it swabbed five carts, three pieces of produce, and three fridge door handles. So, there are definitely germs, but the sample size is low enough that it's dubious to extrapolate the results nationwide.
Nonetheless, these are results from actual grocery stores and most stores have those wipes at the door for a reason. This reason.
Basically everyone has to go to the grocery store at some point -- eating out for every meal every day would be delicious, but totally impossible -- so you should probably take this as an opportunity to steel your resolve to use those cart wipes at the front of the store. Oh, and wash your produce.