Campaign funds were raised for him because people believe in his policy and what he wants to try to do for our country. I don't know what would happen to the funds for his campaign if he dropped out, but it seems to me that that money was given to him to WIN the race, and to give up instead of pushing on for what he believes in doesn't send a strong message for any future races he might be looking at.
Bernie Sanders has raised a very large amount of money, and he seems very passionate in his stance. If he feels the need to continue with his campaign, that is his choice. However, I believe he should seriously consider the consequences of doing so. If he continues to run against Clinton, he keeps his supporters pitted against her, and in the general election this will make it much harder for the Democratic nominee to win. He needs to consolidate with Clinton to ensure that the Democrats get all the votes the two have received during the primaries if he hopes for his party to win.
Yes, Bernie Sanders should continue his presidential campaign. His success has shown what Democrats, especially youth and minorities, want and expect from their candidate, and even if he ultimately loses the nomination to Clinton, this has still shown the Democratic establishment what issues and policies are important to their constituents.
Senator Sanders has stated before that he will continue his campaign until the end of the primary election; and unlike other candidates who have already dropped out of the race, Senator Sanders does have a decent amount of support. Senator Sanders also has a large amount of support from younger generations.