Not sure about the registry but you can use this command in PowerShell to set the sleep and screen shutoff. The monitor-timeout is for the screen and the standby-timeout is for sleep. Change the values to what you want then copy and paste the command into PowerShell and hit enter.
Powercfg /Change monitor-timeout-ac 45
Powercfg /Change monitor-timeout-dc 45
Powercfg /Change standby-timeout-ac 0
Powercfg /Change standby-timeout-dc 0