round a select, to more decimal values I have this query:

SELECT  
POWER( (1 + ( 1.00 ) * (VL_TAXA/100.0) ), ( QT_PRAZODIASU / 252.00000000000 ) ),
POWER( (1 + (( VL_PERCENT_INDEX / 100.0) * (VL_TAXA/100.0)) ), ( -QT_PRAZODIASU / 252.000000000000 ) ),
POWER( (1 + ( VL_PERCENT_INDEX / 100.0) * (VL_TAXA/100.0) ), ( QT_PRAZODIASU / 252.000000000000 ) ),
((    VL_MTM * (
       CASE RISCO_JUROS
         WHEN 'S' THEN POWER( (1 + ( 1.00 ) * (VL_TAXA/100.0) ), ( QT_PRAZODIASU / 252.00000000000 ) )
       ELSE 1.0
       END )
       /
       (
       CASE ID_FRISK
         WHEN 'RELA3' THEN POWER( (1 + ( 1.00 ) * (TAXA_MOEDA3/100.0) ), ( QT_PRAZODIASU / 252.00000000000 ) )
       ELSE 1.0
       END )
       )
       - VL_PRINCIPAL * (      
       CASE ID_MODULO_CALCULO
         WHEN 11 THEN ( 1 + ( TAXA_FWD2 * QT_PRAZODIASC ) / 36000.000000000000 ) / ( 1 + ( TAXA_FWD1 * DC_INI_FWD ) / 36000.000000000000 ) - 1
       ELSE 0.0
       END ) 
 )
       *       
 (
       CASE ID_MODULO_CALCULO
         WHEN 10 THEN POWER( (1 + ( VL_PERCENT_INDEX / 100.0) * (VL_TAXA/100.0) ), ( -QT_PRAZODIASU / 252.000000000000 ) )
       ELSE 1.0
       END 
 ) 

 FROM My_Table WHERE ID_TRANSACAO = '181872'


The result I get is this:

| 1.00501081469 | 0.995014168 | 1.005010815 | -151372478.940930 |   |
| 1.00501081469 | 0.995014168 | 1.005010815 | -151372478.940930 |   |
| 1.00501081469 | 0.995014168 | 1.005010815 | -151372478.940930 |   |


How can I make the second column ('0.995014168') To have more decimals?

I'm trying to convert to decimal, even using round with no success.
Have a look at MS Docs about POWER function:


  Return Types
  Returns the same type as submitted in float_expression. For example, if a decimal(2,0) is submitted as float_expression, the result returned is decimal(2,0).  


CAST left operand as DECIMAL(18, NumDecimals)




-- without CAST

SELECT POWER(1 + (52/100.0) * 0.23, 0.268);
GO



| (No column name) |
| :--------------- |
| 1.03073935       |






-- CAST as DECIMAL(18,12)

SELECT POWER(CAST(1 + (52/100.0) * 0.23 AS DECIMAL(18,12)), 0.268);
GO



| (No column name) |
| :--------------- |
| 1.030739345889   |



dbfiddle here