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 $213.47   11.110%   $237.1865   $237.19   $237.20   $237.20  
  Purchase #2 $231.42   8.257%   $250.5283   $250.53   $250.55   $250.50  
  Purchase #3 $152.91   13.433%   $173.4504   $173.45   $173.45   $173.50  
  Purchase #4 $226.71   8.762%   $246.5743   $246.57   $246.55   $246.60  
  Purchase #5 $117.29   13.161%   $132.7265   $132.73   $132.75   $132.70  
  Purchase #6 $58.33   9.828%   $64.0627   $64.06   $64.05   $64.10  
  Purchase #7 $8.70   13.632%   $9.886   $9.89   $9.90   $9.90  
  7 purchase totals = $1,008.83       $1,114.4147   $1,114.42   $1,114.45   $1,114.50