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 $244.71   8.359%   $265.1653   $265.17   $265.15   $265.20  
  Purchase #2 $32.54   8.229%   $35.2177   $35.22   $35.20   $35.20  
  Purchase #3 $213.60   7.515%   $229.652   $229.65   $229.65   $229.70  
  Purchase #4 $194.77   10.520%   $215.2598   $215.26   $215.25   $215.30  
  Purchase #5 $48.78   12.854%   $55.0502   $55.05   $55.05   $55.10  
  Purchase #6 $53.90   8.289%   $58.3678   $58.37   $58.35   $58.40  
  Purchase #7 $167.38   3.715%   $173.5982   $173.60   $173.60   $173.60  
  7 purchase totals = $955.68       $1,032.3110   $1,032.32   $1,032.25   $1,032.50