Try something like:
Get count of this month, and today:
SELECT SUM(Sales) AS TotalSales,
SUM(CASE WHEN DATEDIFF( m, SaleDate, GETDATE() ) = 0 THEN Sales ELSE 0 END) AS SalesThisMonth,
SUM(CASE WHEN DATEDIFF( d, SaleDate, GETDATE() ) = 0 THEN Sales ELSE 0 END) AS SalesToday
FROM MyTable