Are there hst on prepared food under 4.00 Tim Hortons charge .21cents tax on a product that sell at 3.99?

There's always HST on prepared food under $4.00 in Ontario. However, there is a point of sale rebate available for the provincial component of the HST (8% out of 13%), which was credited to you. ($3.99 x 13% = $0.52)