You can use weight plates or weighted gloves or just round off to the nearest weight you have. The 1RM calculator has a certain degree of error to its calculations, so a small difference in weight will not matter for many exercises. For exercises where you can only lift a small amount of weight, i.e. kickbacks, having odd dumbbells or weight plates/weighted gloves are advisable. If these are not an option for you, just use the closest weight you have that you can lift at least as many times as the reps required.