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 $243.42   7.624%   $261.9783   $261.98   $262.00   $262.00  
  Purchase #2 $104.55   3.428%   $108.134   $108.13   $108.15   $108.10  
  Purchase #3 $10.87   4.756%   $11.387   $11.39   $11.40   $11.40  
  Purchase #4 $104.62   5.561%   $110.4379   $110.44   $110.45   $110.40  
  Purchase #5 $236.65   12.548%   $266.3448   $266.34   $266.35   $266.30  
  Purchase #6 $151.71   7.548%   $163.1611   $163.16   $163.15   $163.20  
  Purchase #7 $131.32   3.709%   $136.1907   $136.19   $136.20   $136.20  
  7 purchase totals = $983.14       $1,057.6338   $1,057.63   $1,057.70   $1,057.60