does couriers like UPS tamper with packages in transit on their way to deliver to you

i feel suspicious about this, albeit, i do have paranoia.....but the last thing i bought online was delivered by UPS, and the package i thought looked like it had been opened and then sealed back closed with sticky tape? but i couldn't prove it...i had no evidence......ive recently bought something else and it is going to be delivered again by UPS this monday.....the delivery guy is a nice guy so i don't exactly suspect him.

but, what should i do?