The taxes estimated by the Tax Calculator on page https://www.ooma.com/savings/ were wildly optimistic for my Ooma Office installation. The Tax Calculator estimated $4.64 per line. The actual taxes were $12.95 per line. Off by roughly a factor of 3x!
Also note that the fax line costs an extra $19.98/mo: $9.99 for the phone number and another $9.99 because it is apparently treated as an additional extension.
Also note that the costs were $9.99/mo and not $9.95/mo as shown on the Ooma Office Pricing Chart http://support.ooma.com/office/ooma-office-pricing-chart#.
Bottom line is not as much savings as I originally thought for Ooma Office. My feeling is that the Ooma Office Sales Department was not as forthcoming as they could have been with the actual costs to be billed, particularly for the fax line.