Similar to the OP, I was mainly a cash-only user except for large purchases (for me, large is anything over ~$50). But about 3 years ago, I switched to a cash-back CC offered by my own bank, one I use for my everyday activities and had recently obtained online banking access earlier in 2014. Makes it really easy to pay the bill.
I began using the CC for many of my previously cash-only purchases, mainly my trips to the supermarket. I still pay cash at the supermarket sometimes, when I buy less than $30. For over $40, I use the CC, and for $30-$40 I sometimes use the CC, sometimes use cash. The result of my increased CC use is that I make only 1 monthly trip to the ATM instead of 2.
But when I go to the supermarket, I no longer have to worry about not having enough cash with me in case something is on sale and I want to load up on it. In that sense, I do spend more when I use my CC. But it isn't like I am eating more food, just being more able to take advantage of something I always buy when it costs less. So, besides the small cash-back I get from using the CC, I save far more money from being able to buy more marked-down items.
For a time in 2014 and 2015, I was able to use my CC to pay my health insurance premium on line. That greatly ramped up my cash-back for a while. But when I changed insurance companies in 2016, my new company did not accept CC to pay monthly premiums.
I have been using my CC to make other payments on line such as my auto insurance (after a check got lost in the mail last year) and car registration renewal.
One place I don't use my CC is to buy gas for my car. Any cash-back would be more than offset by higher per-gallon gas prices for using a CC. I buy gas once very 3 weeks so it isn't a frequent purchase.
I use ACH or online bank check for my monthly bills, so I rarely use my CC even with the added use the last few years. For me, the CC is a tool to enhance my regular spending, not a way to spend more or spend recklessly.