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 $183.26   6.812%   $195.7437   $195.74   $195.75   $195.70  
  Purchase #2 $61.81   6.608%   $65.8944   $65.89   $65.90   $65.90  
  Purchase #3 $246.97   5.299%   $260.0569   $260.06   $260.05   $260.10  
  Purchase #4 $79.27   9.257%   $86.608   $86.61   $86.60   $86.60  
  Purchase #5 $212.26   11.159%   $235.9461   $235.95   $235.95   $235.90  
  Purchase #6 $33.34   7.134%   $35.7185   $35.72   $35.70   $35.70  
  Purchase #7 $88.65   4.437%   $92.5834   $92.58   $92.60   $92.60  
  7 purchase totals = $905.56       $972.5510   $972.55   $972.55   $972.50