Tax Calculation and Round To Cent (for active record and tax >= 2.5)

SELECT COUNT(*)                 AS bil_akaun_dicukaikan,
  SUM(E1.cukai_penggal_sebenar) AS anggaran_cukai
FROM
  (SELECT D1.no_akaun,
    D1.kod_stsakaun,
    D1.nilai_thnn,
    D1.cukai_sms,
    D1.cukai_sms_sen,
    D1.len_cukai_sms_sen,
    D1.nilai_sen,
    to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) AS cukai_b4,
    CASE
      WHEN D1.nilai_sen = 1
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) - 0.01
      WHEN D1.nilai_sen = 2
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) - 0.02
      WHEN D1.nilai_sen = 3
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) + 0.02
      WHEN D1.nilai_sen = 4
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) + 0.01
      WHEN D1.nilai_sen = 5
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen ))
      WHEN D1.nilai_sen = 6
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) - 0.01
      WHEN D1.nilai_sen = 7
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) - 0.02
      WHEN D1.nilai_sen = 8
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) + 0.02
      WHEN D1.nilai_sen = 9
      THEN to_number(SUBSTR (cukai_sms,1, D1.len_cukai_sms_sen )) + 0.01
      ELSE D1.cukai_sms
    END AS cukai_penggal_sebenar
  FROM
    (SELECT C1.no_akaun,
      C1.kod_stsakaun,
      C1.nilai_thnn,
      C1.cukai_sms,
      C1.cukai_sms_sen,
      LENGTH(trim(C1.cukai_sms_sen))                         AS len_cukai_sms_sen,
      SUBSTR(C1.cukai_sms, LENGTH(trim(C1.cukai_sms_sen)),1) AS nilai_sen
    FROM
      (SELECT B1.no_akaun,
        B1.kod_stsakaun,
        B1.nilai_thnn,
        B1.cukai_sms,
        TO_CHAR(B1.cukai_sms,'9999999.99') AS cukai_sms_sen
      FROM
        (SELECT A1.no_akaun,
          A1.kod_stsakaun,
          A1.nilai_thnn,
          A1.kdr_taksiran,
          ROUND(A1.cukai_sms,2) AS cukai_sms
        FROM
          (SELECT no_akaun,
            kod_stsakaun,
            nilai_thnn,
            kdr_taksiran,
            CASE
              WHEN kod_stsakaun = 'T'
              THEN 0
              WHEN (nilai_thnn * KDR_TAKSIRAN/100)/2 < 2.5
              THEN 0
              ELSE (nilai_thnn * KDR_TAKSIRAN/100)/2
            END cukai_sms
          FROM ntharta
          WHERE nilai_thnn >= 0
          AND kdr_taksiran >= 0
          AND no_akaun NOT IN
            ( SELECT no_akaun FROM enpenilaian
            )
  AND kod_stsakaun = 'A'
          ORDER BY no_akaun
          ) A1
        WHERE A1.cukai_sms >= 2.5
) B1
      ) C1
    ) D1
  ) E1 ;