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 $212.91   11.400%   $237.1817   $237.18   $237.20   $237.20  
  Purchase #2 $174.91   10.129%   $192.6266   $192.63   $192.65   $192.60  
  Purchase #3 $30.87   13.675%   $35.0915   $35.09   $35.10   $35.10  
  Purchase #4 $64.34   5.255%   $67.7211   $67.72   $67.70   $67.70  
  Purchase #5 $113.97   6.807%   $121.7279   $121.73   $121.75   $121.70  
  Purchase #6 $53.42   12.605%   $60.1536   $60.15   $60.15   $60.20  
  Purchase #7 $51.32   4.620%   $53.691   $53.69   $53.70   $53.70  
  7 purchase totals = $701.74       $768.1934   $768.19   $768.25   $768.20