The final checkout total should not be a surprise reveal

Comparing two items gets harder when delivery charges or other extras only appear near the end of checkout. By that point, somebody may already have entered an address and spent time choosing options. Some costs do depend on the destination, but a clear estimate can still make the process easier to understand. What should a store explain before asking for personal details? Interested in examples of straightforward checkout design, including how optional extras are presented and whether the final total stays visible throughout.