"To (jest)" means in Polish "This/That is". It's always "to" regardless gender of a noun and "jest" is optional.
For plural nouns you should use "To (są)" (These/Those are). Here "są" is optional too.
And after "To jest/są" you should use a noun in Nominative.
BTW, it is "bluza" not "blusza".
In your example, to is like the noun "this," not the noun determiner "this." The former is saying This is a blouse. The word "this" is the noun itself, in the English translation, so there's no case to match. The latter's case has to match the noun that it determines, ta bluza, this blouse.