This commit is related to BAEL-7113 (#15331)

This commit adds a new test class "RoundNumberToNearestMultipleUnitTest" that suggests multiplе mеthods for rounding up a numbеr to thе nеarеst multiplе of 5 in Java.

core-java-modules/core-java-numbers-conversions/src/test/java/com/baeldung/roundnumbertonearestmultiple/RoundNumberToNearestMultipleUnitTest.java

@@ -0,0 +1,41 @@
+package com.baeldung.roundnumbertonearestmultiple;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class RoundNumberToNearestMultipleUnitTest {
+
+    public static int originalNumber = 18;
+    public static int expectedRoundedNumber = 20;
+    public static int nearest = 5;
+
+    @Test
+    public void givenNumber_whenUsingBasicMathOperations_thenRoundUpToNearestMultipleOf5() {
+
+        int roundedNumber = (originalNumber % nearest == 0) ? originalNumber : ((originalNumber / nearest) + 1) * nearest;
+        assertEquals(expectedRoundedNumber, roundedNumber);
+    }
+
+    @Test
+    public void givenNumber_whenUsingMathCeil_thenRoundUpToNearestMultipleOf5() {
+
+        int roundedNumber = (int) (Math.ceil(originalNumber / (float) (nearest)) * nearest);
+        assertEquals(expectedRoundedNumber, roundedNumber);
+    }
+
+    @Test
+    public void givenNumber_whenUsingMathRound_thenRoundUpToNearestMultipleOf5() {
+
+        int roundedNumber = Math.round(originalNumber / (float) (nearest)) * nearest;
+        assertEquals(expectedRoundedNumber, roundedNumber);
+    }
+
+    @Test
+    public void givenNumber_whenUsingMathFloor_thenRoundUpToNearestMultipleOf5() {
+
+        int roundedNumber = (int) (Math.floor((double) (originalNumber + nearest / 2) / nearest) * nearest);
+        assertEquals(expectedRoundedNumber, roundedNumber);
+    }
+
+}