Here's the specific quote, discussing how the Scottish armies would not let the defeated King of Norway bury his men until he paid $10,000. What are these dollars?
DUNCAN
Great happiness!
ROSS
That now / Sweno, the Norways' king, craves composition. / Nor would we deign him burial of his men / Till he disbursed at Saint Colme’s Inch / Ten thousand dollars to our general use.
Dollar is originally an anglicisation of the German word thaler (taler in more modern spelling). The silver mines of Joachimsthal in the German-speaking part of Bohemia led to the creation of a silver coin called thaler (later taler) in 1519, which became de facto standard coin over much of Europe, as local rulers often restricted minting of their own coins to either save on silver or to create deflation, increasing the value of their own stocks of coin. The Thaler had 25,98 grams of pure silver.
The most famous thaler coin was the Spanish 8-real coin, also called dollar (and the more famous name piece of eight in pirate lore), which was de facto standard currency of the New World, which is the cause of the US currency's name.
The Spanish dollar came into existence in 1598 and Sweden, Norway and Denmark minted daler, their own version of thaler. By the time MacBeth was first performed in 1611, the Spanish dollar was pretty much the most common silver coin in the world, due to the vast reserves of silver the Spanish had found in the New World.
Shakespeare's contemporaries would most likely know what a dollar was, however, the 11th century MacBeth would not, as it had not been created then.
Macbeth isn't just a play about witchcraft, murder, and succession, it also involves Shakespeare taking the opportunity to play up all things Scottish with the accession of James VI of Scotland to the English throne. For example, the Witches prophesy that Banquo's descendants will be kings and some 'will twofold balls and treble sceptres carry', thus presenting James' accession to the English (and Irish) thrones as preordained. Never hurts to have the King well disposed to you.
The rather specific reference to dollars, however, is playing up Scottishness in another way. While we associate dollars in the Renaissance with the Czech joachimsthaler, widely circulated and the basis for other German thalers/dollars, James VI issued a run of well circulated Scottish coins known as the 'thistle dollar' since they had a thistle stamped on them. Thus, the reference to dollars is a bit of anachronistic Scottish localisation on Shakespeare's part. 11th C Macbeth wouldn't have known what a Scottish dollar was but the 16th C audience would have.