As used in paragraph (c) of Section 181.05, "sales made in the City" means:
(a) All sales of tangible personal property which is delivered within the City regardless of where title passes if shipped or delivered from a stock of goods within the City.
(b) All sales of tangible personal property which is delivered within the City regardless of where title passes even though transported from a point outside the City if the taxpayer is regularly engaged through its own employees in the solicitation or promotion of sales within the City and the sales result from such solicitation or promotion.
(c) All sales of tangible personal property which is shipped from a place within the City to purchasers outside of the City regardless of where title passes if the taxpayer is not, through its own employees, regularly engaged in the solicitation or promotion of sales at the place where delivery is made.
(1969 Code 92.06)