Is it ok to alter the clothes i wear for work?

I work at a small private owned boutique in a small town. Our dress code (if u can even call it that..) is pretty much whatever u want to wear, then something from the store. We mainly sell tshirts and sport theme shirts. None of its really my style though.. do you think itd be okay to get a sweatshirt and cute the neck hem out to make an off the shoulder top, or similar tiny tweaks to clothes? Of course, the clothes i wear to work ive bought, so they are my property, not the stores