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 $219.34   11.261%   $244.0399   $244.04   $244.05   $244.00  
  Purchase #2 $72.81   12.615%   $81.995   $82.00   $82.00   $82.00  
  Purchase #3 $231.82   12.678%   $261.2101   $261.21   $261.20   $261.20  
  Purchase #4 $54.58   8.397%   $59.1631   $59.16   $59.15   $59.20  
  Purchase #5 $78.41   12.488%   $88.2018   $88.20   $88.20   $88.20  
  Purchase #6 $118.96   5.224%   $125.1745   $125.17   $125.15   $125.20  
  Purchase #7 $192.30   12.158%   $215.6798   $215.68   $215.70   $215.70  
  7 purchase totals = $968.22       $1,075.4642   $1,075.46   $1,075.45   $1,075.50