If you look at the IRS table, https://www.irs.gov/pub/irs-pdf/p15.pdf#page=42 , you can see the percentage method and wage bracket methods are not equivalent. For example, if I am a single person on a weekly payroll period earning $44 a week, according to table 1 on page 45, I should get taxed 0%. But according to wage bracket table on page 47, taxes don't start until $55.
That means if I make $55, according to the percentage method, I will be taxed $5.50, and according to the wage bracket table I will be taxed $0. What is going on here?