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 $241.35   8.447%   $261.7368   $261.74   $261.75   $261.70  
  Purchase #2 $217.50   12.457%   $244.594   $244.59   $244.60   $244.60  
  Purchase #3 $60.34   10.134%   $66.4549   $66.45   $66.45   $66.50  
  Purchase #4 $221.73   13.712%   $252.1336   $252.13   $252.15   $252.10  
  Purchase #5 $133.97   9.147%   $146.2242   $146.22   $146.20   $146.20  
  Purchase #6 $46.49   9.526%   $50.9186   $50.92   $50.90   $50.90  
  Purchase #7 $91.85   6.391%   $97.7201   $97.72   $97.70   $97.70  
  7 purchase totals = $1,013.23       $1,119.7822   $1,119.77   $1,119.75   $1,119.70