By John S. McClenahen Philanthropy in the U.S. takes many forms, from individuals making $5 and $10 gifts to companies that take part in countrywide projects, such as helping develop a computer-based network to improve the distribution of food to those in need. And it looks as if individuals, who along with bequests and foundations, account for 90% of all gift giving, and companies, which account for the remaining 10%, will be doing more, not less, during the next five years. Charitable gift giving in the U.S. is expected to continue to grow at about a 7% annual rate between now and the year 2005, calculates Merrill Lynch & Co., New York. In dollar terms, charitable contributions now total about $190 billion annually. Merrill Lynch believes that by the year 2015 they could top half a trillion dollars.