              "UNSET"
                            "ECONOMICAL"
                            "CONSERVATIVE"

Result:
"txid"                  (string) The transaction id.

Examples:
> bitcoin-cli sendtoaddress "1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd" 0.1
> bitcoin-cli sendtoaddress "1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd" 0.1 "donation" "seans outpost"
> bitcoin-cli sendtoaddress "1M72Sfpbz1BPpXFHz9m3CdqATR44Jvaydd" 0.1 "" "" true
> curl --user myusername --data-binary '{"jsonrpc": "1.0", "id":"curltest", "method": "s