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 $59.91   11.855%   $67.0123   $67.01   $67.00   $67.00  
  Purchase #2 $153.36   6.413%   $163.195   $163.20   $163.20   $163.20  
  Purchase #3 $126.47   5.321%   $133.1995   $133.20   $133.20   $133.20  
  Purchase #4 $209.30   6.183%   $222.241   $222.24   $222.25   $222.20  
  Purchase #5 $27.87   9.854%   $30.6163   $30.62   $30.60   $30.60  
  Purchase #6 $242.31   8.383%   $262.6228   $262.62   $262.60   $262.60  
  Purchase #7 $45.33   5.274%   $47.7207   $47.72   $47.70   $47.70  
  7 purchase totals = $864.55       $926.6076   $926.61   $926.55   $926.50