This is not too much. Most of modern 5V devices are supposed to support charging over USB.
For example, according to USB wiki page: "The specification provides for no more than 5.25 V and no less than 4.75 V (5 V ± 5%)
So your charger even meets USB requirements
In fact usually the charging process is controlled internally by the device, so this internal controller will limit the charging current and stop charging if needed.