Do not issue correct change

It has happened three times now, the first time I was out the store when I checked my change and found it incorrect, Second time complained to the manager and he did not apologise he just said he will look into it. Third time I complained to the store manager who leaned against the counter and yes said he will look into it.<br> So if you do not check your change they will rip you off One is understandable but THREE TIMES