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 $197.36   4.357%   $205.959   $205.96   $205.95   $206.00  
  Purchase #2 $205.44   10.591%   $227.1982   $227.20   $227.20   $227.20  
  Purchase #3 $188.63   4.667%   $197.4334   $197.43   $197.45   $197.40  
  Purchase #4 $63.67   9.411%   $69.662   $69.66   $69.65   $69.70  
  Purchase #5 $58.77   9.224%   $64.1909   $64.19   $64.20   $64.20  
  Purchase #6 $199.66   9.543%   $218.7136   $218.71   $218.70   $218.70  
  Purchase #7 $38.92   13.676%   $44.2427   $44.24   $44.25   $44.20  
  7 purchase totals = $952.45       $1,027.3998   $1,027.39   $1,027.40   $1,027.40