Formatting Text Field As HH:MM:SS
You can use this
Schema (MySQL v8.0)
CREATE TABLE Table1
    (`salesTime` varchar(7))
;
    
INSERT INTO Table1
    (`salesTime`)
VALUES
    ('0:05:58'),
    ('0:00:00'),
    ('0:31:54'),
    ('0:23:26')
;


Query #1
SELECT SEC_TO_TIME( SUM( TIME_TO_SEC(TIME_FORMAT(`salesTime`, &quot;%H:%i:%s&quot;))))  FROM Table1;

| SEC_TO_TIME( SUM( TIME_TO_SEC(TIME_FORMAT(`salesTime`, &quot;%H:%i:%s&quot;)))) |
| --------------------------------------------------------------------- |
| 01:01:18                                                              |


View on DB Fiddle
But TIME can only have the maximum of 838:59:59, if your SUM get bigger, you need to convert the seconds also into dd.hh:mm:ss