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 $213.66   5.162%   $224.6891   $224.69   $224.70   $224.70  
  Purchase #2 $165.81   5.499%   $174.9279   $174.93   $174.95   $174.90  
  Purchase #3 $43.94   5.514%   $46.3629   $46.36   $46.35   $46.40  
  Purchase #4 $242.50   8.738%   $263.6897   $263.69   $263.70   $263.70  
  Purchase #5 $188.52   5.544%   $198.9715   $198.97   $198.95   $199.00  
  Purchase #6 $79.89   4.486%   $83.4739   $83.47   $83.45   $83.50  
  Purchase #7 $127.49   12.527%   $143.4607   $143.46   $143.45   $143.50  
  7 purchase totals = $1,061.81       $1,135.5757   $1,135.57   $1,135.55   $1,135.70