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 $104.92   8.245%   $113.5707   $113.57   $113.55   $113.60  
  Purchase #2 $230.42   13.868%   $262.3746   $262.37   $262.35   $262.40  
  Purchase #3 $226.28   10.546%   $250.1435   $250.14   $250.15   $250.10  
  Purchase #4 $214.28   10.406%   $236.578   $236.58   $236.60   $236.60  
  Purchase #5 $6.36   11.510%   $7.092   $7.09   $7.10   $7.10  
  Purchase #6 $59.76   11.604%   $66.6946   $66.69   $66.70   $66.70  
  Purchase #7 $247.94   6.771%   $264.728   $264.73   $264.75   $264.70  
  7 purchase totals = $1,089.96       $1,201.1814   $1,201.17   $1,201.20   $1,201.20