Six-bits is commonly understood in the United States of America to be 3 quarters or about 75 cents. The word “bit” a colloquial expression long meant, in England, any coin of a low denomination. In early America, “bit” was used for some Spanish and Mexican coins that circulated and were worth one-eighth of a peso, or about 12 and one-half cents.
So, in the U.S., two bits has routinely equaled about 25 cents, and four bits has typically been considered to be about 50 cents. In sequence, it therefore means that 75 cents is six-bits and eight-bits is a dollar.