My Point of View

This is how to check NULL or empty input values for a date column. Currently NULL or empty values produces ‘1900-01-01’ value which is not acceptable.

DECLARE @InputDate DATE

--set input to spaces
SET @InputDate = ''
--don't want 1900-01-01 output, instead NULL value
SELECT ISNULL(NULLIF(@InputDate, ''), NULL) AS InputDateSpaces

--set input to null
SET @InputDate = NULL
--don't want 1900-01-01 output, instead NULL value
SELECT ISNULL(NULLIF(@InputDate, ''), NULL) AS InputDateNULL

--set input to date
SET @InputDate = '2021-06-25'
--don't want 1900-01-01 output, instead date value
SELECT ISNULL(NULLIF(@InputDate, ''), NULL) AS InputDateRealDate

These are the results;

This is how to run a SQL Query where you have two date columns and like to see if your date falls between those columns;

SELECT * FROM FiscalCalendarRef
WHERE 1=1
AND '2021-09-13' BETWEEN StartDate AND EndDate

If EndDate column is defined as NULL, you can change it like this;

SELECT * FROM FiscalCalendarRef
WHERE 1=1
AND '2021-09-13' BETWEEN StartDate AND COALESCE(EndDate, GETDATE())

This is my sample data.

This is how we can achieve expected results in SQL Server, assuming Values column is of NVARCHAR type;

CEILING(ROUND(CONVERT(DECIMAL(10,2), Values), 0))