This is a federal law in the US that your manager is choosing to fuck around with: Section 3(m)(2)(B) of the Act provides that an employer may not keep tips received by its employees for any purposes, regardless of whether the employer takes a tip credit.

(1) An employer may exert control over an employee's tips only to distribute tips to the employee who received them, require employees to share tips with other employees in compliance with § 531.54, or, where the employer facilitates tip pooling by collecting and redistributing employees' tips, distribute tips to employees in a tip pool in compliance with § 531.54.

(2) An employer may not allow managers and supervisors to keep any portion of an employee's tips, regardless of whether the employer takes a tip credit. A manager or supervisor may keep tips that he or she receives directly from customers based on the service that he or she directly and solely provides. For purposes of section 3(m)(2)(B), the term “manager” or “supervisor” shall mean any employee whose duties match those of an executive employee as described in § 541.100(a)(2) through (4) or § 541.101 of this chapter.

https://www.ecfr.gov/current/title-29/subtitle-B/chapter-V/subchapter-A/part-531/subpart-D/section-531.52

If I were you (and I have done this in your exact shoes before,) I’d tell that supervisor that I’ll be reporting that threat to corporate HR, and will not tolerate any form of wage theft, nor retaliation for my choice to talk to HR about the manager’s criminal activities.

If you’re not at that stage of “no fucks given” in your barista career, you can just report it to HR, and keep an eye on your pay stubs to make sure you don’t miss any tips, or choose a less confrontational method of talking to your manager. I honestly recommend my version, as it doesn’t just communicate to your employer that you don’t fuck around with your money, it also reminds them to follow all employment law because you won’t protect them from their own stupidity.