根据指定的保留小数位进行四舍五入

//src需要进行计算的原数值

//nbit保留位数

double Rounding(double src, int nbit)

{


CString strDate;
strDate.Format("%lf", src);
int nPos = strDate.Find('.');
CString strVal = strDate.Left(nPos+nbit+1);
CString strBitVal = strDate.Mid(nPos+nbit+1, 1);
int nTemp = _ttoi(strBitVal);
double dSize = 0;
if(nTemp >=5 )
{
int nValItem=1;
for ( int i=0; i<nbit; i++ )
{
nValItem *= 10;
}
dSize =(double)1/nValItem;
}


return _tstof(strVal)+dSize;
}