Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $68.36   11.202%   $76.0177   $76.02   $76.00   $76.00  
  Purchase #2 $86.69   7.693%   $93.3591   $93.36   $93.35   $93.40  
  Purchase #3 $22.34   13.601%   $25.3785   $25.38   $25.40   $25.40  
  Purchase #4 $169.37   8.102%   $183.0924   $183.09   $183.10   $183.10  
  Purchase #5 $10.27   6.773%   $10.9656   $10.97   $10.95   $11.00  
  Purchase #6 $160.59   12.654%   $180.9111   $180.91   $180.90   $180.90  
  Purchase #7 $201.35   12.668%   $226.857   $226.86   $226.85   $226.90  
  7 purchase totals = $718.97       $796.5814   $796.59   $796.55   $796.70