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 $119.69   6.246%   $127.1658   $127.17   $127.15   $127.20  
  Purchase #2 $66.92   4.633%   $70.0204   $70.02   $70.00   $70.00  
  Purchase #3 $61.71   8.339%   $66.856   $66.86   $66.85   $66.90  
  Purchase #4 $196.64   5.535%   $207.524   $207.52   $207.50   $207.50  
  Purchase #5 $186.30   13.269%   $211.0201   $211.02   $211.00   $211.00  
  Purchase #6 $114.28   6.789%   $122.0385   $122.04   $122.05   $122.00  
  Purchase #7 $71.89   7.783%   $77.4852   $77.49   $77.50   $77.50  
  7 purchase totals = $817.43       $882.1100   $882.12   $882.05   $882.10