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 $62.81   4.552%   $65.6691   $65.67   $65.65   $65.70  
  Purchase #2 $50.73   5.722%   $53.6328   $53.63   $53.65   $53.60  
  Purchase #3 $22.37   4.788%   $23.4411   $23.44   $23.45   $23.40  
  Purchase #4 $247.59   7.712%   $266.6841   $266.68   $266.70   $266.70  
  Purchase #5 $116.81   7.662%   $125.76   $125.76   $125.75   $125.80  
  Purchase #6 $213.53   4.159%   $222.4107   $222.41   $222.40   $222.40  
  Purchase #7 $179.93   6.185%   $191.0587   $191.06   $191.05   $191.10  
  7 purchase totals = $893.77       $948.6565   $948.65   $948.65   $948.70