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 $61.70   10.137%   $67.9545   $67.95   $67.95   $68.00  
  Purchase #2 $217.40   5.389%   $229.1157   $229.12   $229.10   $229.10  
  Purchase #3 $163.41   5.230%   $171.9563   $171.96   $171.95   $172.00  
  Purchase #4 $53.73   13.561%   $61.0163   $61.02   $61.00   $61.00  
  Purchase #5 $207.69   3.127%   $214.1845   $214.18   $214.20   $214.20  
  Purchase #6 $74.38   4.857%   $77.9926   $77.99   $78.00   $78.00  
  Purchase #7 $60.70   12.103%   $68.0465   $68.05   $68.05   $68.00  
  7 purchase totals = $839.01       $890.2664   $890.27   $890.25   $890.30