Travel agency tickets are settled between agency and airline via Airline Reporting Corp (ARC) or maybe BSP. ARC framework allows for travel agency tickets to be voided by end of next business day. As mentioned in my prior post, tickets issued on Friday can be voided as late as Monday evening Eastern time. Other country Expedia sites may/may not offer this.
US travel agents including Priceline and others such as corporate travel agencies can void under this framework. Whether they offer to customers (and at no cost) is a different story.