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 $88.56   7.536%   $95.2339   $95.23   $95.25   $95.20  
  Purchase #2 $76.86   10.811%   $85.1693   $85.17   $85.15   $85.20  
  Purchase #3 $55.68   10.423%   $61.4835   $61.48   $61.50   $61.50  
  Purchase #4 $44.44   5.561%   $46.9113   $46.91   $46.90   $46.90  
  Purchase #5 $200.57   12.704%   $226.0504   $226.05   $226.05   $226.10  
  Purchase #6 $225.38   8.561%   $244.6748   $244.67   $244.65   $244.70  
  Purchase #7 $210.44   5.665%   $222.3614   $222.36   $222.35   $222.40  
  7 purchase totals = $901.93       $981.8846   $981.87   $981.85   $982.00