Wow. Those are much better, closer-to-home, examples than I would have chosen. Great job!Postal rates are floor functions. Letters between weights w1 and w2 will cost c1 cents; those between weights w2 and w3 will cost c2 cents, etc.
Tax tables are another floor function. If your taxable income is between t1 and t2 then you pay p1; if between t2 and t3 then you pay p2, etc.
Any time you go somewhere and you have to pay d dollars for every hour or portion of an hour for boating, bowling, or laser tag is a ceiling function--you played for 40 minutes means you pay the same price as a full hour.