"I need a dime" is a phrase commonly used to express the need for money or to make a call from a payphone. However, there are several synonyms for this phrase that can be used in different contexts. "I need cash" is a broader phrase that can indicate a need for any amount of money. "I need some spare change" specifically refers to small denominations of coins. "I need a buck" is another informal way of saying that money is needed. Additionally, "I need to borrow some funds" or "I need financial assistance" can be used in more formal contexts. No matter which synonym is used, the message remains the same - a need for money or support.