py/formatfloat: Workaround (fix?) incorrect rounding for %f format.

py/formatfloat.c

@@ -308,7 +308,9 @@ int mp_format_float(FPTYPE f, char *buf, size_t buf_size, char fmt, int prec, ch
     }
 
     // Round
-    if (f >= FPCONST(5.0)) {
+    // If we print non-exponential format (i.e. 'f'), but a digit we're going
+    // to round by (e) is too far away, then there's nothing to round.
+    if ((org_fmt != 'f' || e <= 1) && f >= FPCONST(5.0)) {
         char *rs = s;
         rs--;
         while (1) {