Detect Tampering on Posted Package

I need a method to test if a small parcel or box has been opened after being posted, specifically to determine if the sender tampered with it by cutting and retaping it to simulate post office tampering. The solution should provide clear and reliable evidence of such tampering. Ideal skills include expertise in tamper-evident packaging, forensic analysis, or security seals. Please suggest a practical approach or device to ensure evidence of tampering is unmistakable.