A pair of DATEADD / DATEDIFF will round the date until the last midnight:
SELECT a , b FROM myTbl WHERE DATE BETWEEN DATEADD(day,DATEDIFF(day,0,GETDATE()),0) and GETDATE()
Alternatively, if you are using SQL Server 2008 or later:
SELECT a , b FROM myTbl WHERE DATE BETWEEN CONVERT(date,GETDATE()) and GETDATE()
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