It depends on how sensible your dd is, but I would say most 10 year olds are more than capable of being left for an hour or so.
Mine were both left from this age. We had rules about no cooking, not answering the door etc.
The only issue we had was one Sunday, when ds1 was 10, he didn't want to come to church so we agreed he could stay home, he'd stayed home alone before. Somehow he became quite convinced that he could hear someone moving around in the house (thought it was a burglar) and hid under the dining table, tried to phone me but I had phone switched to silent because we were in church. He was beside himself when we got home which made me realise that maybe he wasn't as ready as I thought he was. I also learned to put my phone on vibrate and have it in my pocket so I could answer him in future!
