A store prices an item in dollars and cents so that when 4% sales tax is added, no rounding is necessary because the result is exactly $n$ dollars where $n$ is a positive integer. The smallest value of $n$ is
$\text{(A)} \ 1 \qquad \text{(B)} \ 13 \qquad \text{(C)} \ 25 \qquad \text{(D)} \ 26 \qquad \text{(E)} \ 100$
Say that the price of the item in cents is $x$ (so $x$ is a positive integer as well). The sales tax would then be $\frac{x}{25}$, so $n=\frac{1}{100}\left( x+\frac{x}{25}\right)=\frac{26x}{2500}=\frac{13x}{1250}$. 
Since $x$ is positive integer, the smallest possible integer value for $n=\frac{13x}{1250}$ occurs when $x=1250$, which gives us the answer $\fbox{\text{(B)13}}$.