Smallest resolution directly out of Sense Export is 1 Hour. That’s an option, along with Day, on the last step of Export, regardless of Trend export interval (Day, Week, Month, Year, Bill).
If you want smaller resolution data, you’ll need to use something like Home Assistant to sample data via the Sense informal API and store. The default Sense integration in Home Assistant samples at 1x per minute which is the max sample rate for the Sense API. Once you have collected the data in Home Assistant, there are numerous ways to access, analyze and export it.