$$ \text{Sales tax} = \text{Purchase price} \times \text{Sales tax rate} $$
In this case, the purchase price is $1500 and the sales tax rate is 5%, or 0.05. Therefore, the sales tax is:
$$ \text{Sales tax} = \$1500 \times 0.05 = \$75 $$
So, Robert paid a total of:
$$ \text{Total cost} = \text{Purchase price} + \text{Sales tax} = \$1500 + \$75 = \$1575 $$
Therefore, Robert paid $1575 for the car.
