Alternate approach to http://johannes.tax/Inline_unit_tests_in_Clojure.html

inline_testing.clj

(defn round5
  "Round to the closest positive multiple of 5.
  Negative numbers round to 0, which is not
  considered a multiple of 5."
 {:test (fn [] (let [roundsto (fn [e] #(= e (round5 %)))]
                  (testing "Negative numbers"
                    (is (every? (roundsto 0) (range -20 0))))
                  (testing "Positive numbers rounding to 5"
                    (is (every? (roundsto 5) (range 0 8))))
                  (testing "Positive numbers rounding not to 5"
                    (is (every? (roundsto 10) (range 8 13)))
                    (is (every? (roundsto 20) (range 18 23)))
                    (is (= 1020 (round5 1022))))))} 
  [n]
  (cond (< n 0)
        0
        (< n 8)
        5
        :else
        (let [remainder (rem n 5)
              quotient (quot n 5)]
          (* 5 (+ quotient
                  (if (<= remainder 2)
                      0
                      1))))))