[tex]\begin{array}{ccc}10\ lb&-&\$6.55\\\\1\ lb&-&\$ x\end{array}\ \ \ |cross\ multiply\\\\\\\\10\cdot x=1\cdot6.55\\\\10x=6.55\ \ \ \ |divide\ both\ sides\ by\ 10\\\\x=\frac{6.55}{10}\\\\x=0.65\underline{5}\approx\boxed{\$0.66}\\[/tex]
If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up (+1).