Fix ROUNDUP and ROUNDDOWN for negative number

Closes #1417

CHANGELOG.md

@@ -15,6 +15,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 ### Fixed
 
 - Fix ROUNDUP and ROUNDDOWN for floating-point rounding error [#1404](https://github.com/PHPOffice/PhpSpreadsheet/pull/1404)
+- Fix ROUNDUP and ROUNDDOWN for negative number [#1417](https://github.com/PHPOffice/PhpSpreadsheet/pull/1417)
 - Fix loading styles from vmlDrawings when containing whitespace [#1347](https://github.com/PHPOffice/PhpSpreadsheet/issues/1347)
 - Fix incorrect behavior when removing last row [#1365](https://github.com/PHPOffice/PhpSpreadsheet/pull/1365)
 - MATCH with a static array should return the position of the found value based on the values submitted [#1332](https://github.com/PHPOffice/PhpSpreadsheet/pull/1332)

src/PhpSpreadsheet/Calculation/MathTrig.php

@@ -1139,9 +1139,7 @@ public static function ROUNDUP($number, $digits)
 
         if ((is_numeric($number)) && (is_numeric($digits))) {
             if ($number < 0.0) {
-                $significance = pow(10, (int) $digits);
-
-                return floor($number * $significance) / $significance;
+                return round($number - 0.5 * pow(0.1, $digits), $digits, PHP_ROUND_HALF_DOWN);
             }
 
             return round($number + 0.5 * pow(0.1, $digits), $digits, PHP_ROUND_HALF_DOWN);
@@ -1167,9 +1165,7 @@ public static function ROUNDDOWN($number, $digits)
 
         if ((is_numeric($number)) && (is_numeric($digits))) {
             if ($number < 0.0) {
-                $significance = pow(10, (int) $digits);
-
-                return ceil($number * $significance) / $significance;
+                return round($number + 0.5 * pow(0.1, $digits), $digits, PHP_ROUND_HALF_UP);
             }
 
             return round($number - 0.5 * pow(0.1, $digits), $digits, PHP_ROUND_HALF_UP);

tests/data/Calculation/MathTrig/ROUNDDOWN.php

@@ -71,6 +71,16 @@
         2.26 + 2.94,
         2,
     ],
+    [
+        -4.44,
+        -4.4400,
+        2,
+    ],
+    [
+        -5.20,
+        -2.26 - 2.94,
+        2,
+    ],
     [
         '#VALUE!',
         'ABC',

tests/data/Calculation/MathTrig/ROUNDUP.php

@@ -66,11 +66,21 @@
         4.4400,
         2,
     ],
+    [
+        -4.44,
+        -4.4400,
+        2,
+    ],
     [
         5.20,
         2.26 + 2.94,
         2,
     ],
+    [
+        -5.20,
+        -2.26 - 2.94,
+        2,
+    ],
     [
         '#VALUE!',
         'ABC',