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 $222.60   5.458%   $234.7495   $234.75   $234.75   $234.70  
  Purchase #2 $205.39   3.249%   $212.0631   $212.06   $212.05   $212.10  
  Purchase #3 $51.26   13.506%   $58.1832   $58.18   $58.20   $58.20  
  Purchase #4 $146.89   5.359%   $154.7618   $154.76   $154.75   $154.80  
  Purchase #5 $155.31   3.462%   $160.6868   $160.69   $160.70   $160.70  
  Purchase #6 $169.48   6.434%   $180.3843   $180.38   $180.40   $180.40  
  Purchase #7 $13.76   11.762%   $15.3785   $15.38   $15.40   $15.40  
  7 purchase totals = $964.69       $1,016.2072   $1,016.20   $1,016.25   $1,016.30