code: public static Set<String> getRoundingNames(String... providers) {
          return Optional.ofNullable(monetaryRoundingsSingletonSpi()).orElseThrow(
                  () -> new MonetaryException("No MonetaryRoundingsSpi loaded, query functionality is not available."))
                  .getRoundingNames(providers);
      }
docs: Allows to access the names of the current defined roundings.
  
  @param providers the providers and ordering to be used. By default providers and ordering as defined in
  #getDefaultProviders is used.
  @return the set of custom rounding ids, never {@code null}.