Authors consider continuous linear time invariant multivariable systems affected by external bounded deterministic piecewise continuous disturbances that admit Fourier series decomposition. On top of that, for every component of the disturbance, the sum of the harmonics amplitudes absolute values is supposed to be bounded by a known number. The problem is to design a linear state or output feedback controller that guarantees a given accuracy characterized by the maximum deviation of the controlled variables from zero during the system steady state. To solve the problem, authors use well-known LQ- and H_infinity-optimization procedures for which the accurate rules for choosing the weighting matrices of the corresponding quadratic cost are determined. The efficiency of the proposed design technique is validated by applying it to the controller design problem for an electromechanical system.