Your time profile is configurable, in which you specify the date ranges of your quarters and years.
Because of this, if your customer chose any date within the respective quarter or year, the tool would display the values within that quarter or year on a report.
If you wanted to recommend a date for your customer to pick, they could make it their business practice to always load to the last date of their desired time bucket.
Furthermore, your key figures will always have a base planning level. This base planning level will have a configured root level for the time dimension. So for your respective key figure you could choose your configured quarterly time level. This method could systematically force the value to only surface on reports at a quarterly level.