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 $59.39   3.674%   $61.572   $61.57   $61.55   $61.60  
  Purchase #2 $34.71   4.364%   $36.2247   $36.22   $36.20   $36.20  
  Purchase #3 $121.63   7.151%   $130.3278   $130.33   $130.35   $130.30  
  Purchase #4 $190.66   12.607%   $214.6965   $214.70   $214.70   $214.70  
  Purchase #5 $113.49   5.686%   $119.943   $119.94   $119.95   $119.90  
  Purchase #6 $217.98   3.302%   $225.1777   $225.18   $225.20   $225.20  
  Purchase #7 $73.45   6.162%   $77.976   $77.98   $78.00   $78.00  
  7 purchase totals = $811.31       $865.9177   $865.92   $865.95   $865.90