YOU SAID:
I'm going to the groceries shop tonight
INTO JAPANESE
私は今夜食料品店に行く
BACK INTO ENGLISH
I will go to a grocery store tonight
INTO JAPANESE
私は今夜食料品店に行きます
BACK INTO ENGLISH
I will go to a grocery store tonight.
INTO JAPANESE
私は今夜食料品店に行きます。
BACK INTO ENGLISH
I will go to a grocery store tonight.
That didn't even make that much sense in English.