10 cents
A decidollar is a term that represents one-tenth of a dollar, or 10 cents. The prefix "deci-" signifies a factor of one-tenth in the metric system. Therefore, there are 0.1 dollars in a decidollar.
Neither
Penny: Centidollar Dime: Decidollar Ten dollar bill: Decadollar 100 dollar bill: Hectodollar 1,000 dollar bill: Kilodollar