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 $67.67   13.724%   $76.957   $76.96   $76.95   $77.00  
  Purchase #2 $204.34   9.582%   $223.9199   $223.92   $223.90   $223.90  
  Purchase #3 $99.71   8.212%   $107.8982   $107.90   $107.90   $107.90  
  Purchase #4 $222.62   6.445%   $236.9679   $236.97   $236.95   $237.00  
  Purchase #5 $53.48   8.544%   $58.0493   $58.05   $58.05   $58.00  
  Purchase #6 $51.56   3.312%   $53.2677   $53.27   $53.25   $53.30  
  Purchase #7 $249.29   7.812%   $268.7645   $268.76   $268.75   $268.80  
  7 purchase totals = $948.67       $1,025.8245   $1,025.83   $1,025.75   $1,025.90