on figuring out the worth of Roman currency.

As can be seen in that piece, you can roughly figure the value of the denarius in terms of modern buying power at about $20. Now, since a denarius was worth 4 sestertii, let's look at some of the figures in Calpurnia's post:

Cicero's house on the Palatine: 2 million sestertii= 500,000 denarii= $1 million
Atticus' inheritance from his uncle: 10 million sestertii= 2.5 million denarii= $50 million
price Caesar paid for the land for his forum: 60 million sestertii= 15 million denarii= $300 million

Other sources give the annual pay of standard legionaire at the time of Augustus through Domitian as 225 denarii or 900 HS or about $4,500. Bear in mind that this was often increased by share of booty in wars and donatives by emperors on their accessions.