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 $223.62   5.602%   $236.1472   $236.15   $236.15   $236.10  
  Purchase #2 $225.55   11.372%   $251.1995   $251.20   $251.20   $251.20  
  Purchase #3 $214.88   9.314%   $234.8939   $234.89   $234.90   $234.90  
  Purchase #4 $95.48   12.787%   $107.689   $107.69   $107.70   $107.70  
  Purchase #5 $216.91   9.614%   $237.7637   $237.76   $237.75   $237.80  
  Purchase #6 $166.76   5.368%   $175.7117   $175.71   $175.70   $175.70  
  Purchase #7 $241.81   5.123%   $254.1979   $254.20   $254.20   $254.20  
  7 purchase totals = $1,385.01       $1,497.6029   $1,497.60   $1,497.60   $1,497.60