Replace value based on previous row / next row depending on conditions
Add this composite index if you don't already have it -- it should probably be the PRIMARY KEY.

INDEX(company_id, date_time)


Run this a few times (until it stops modifying any rows)

UPDATE    tbl a
    JOIN  tbl b
       ON  b.company_id = a.company_id
      AND  b.date_time  = a.date_time + INTERVAL 1 MINUTE
    SET a.price_open = b.price_open
    WHERE  a.price_open  = 0.00
      AND  b.price_open != 0.00; 


In case I am wrong, suggest you copy the table over for testing:

CREATE TABLE tbl LIKE real_tbl;
ALTER TABLE tbl DROP PRIMARY KEY,
                ADD  PRIMARY KEY(company_id, date_time);  -- if needed
INSERT INTO tbl SELECT * FROM real_tbl;
run the update a few times
check the values
if satisfied, ...
RENAME TABLE real_tbl TO old, tbl TO real_tbl;
DROP TABLE old;


On the presumption that your SELECTs will be company-centric, it is better to have PRIMARY KEY(co, dt) than (dt, co).