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 $176.63   5.685%   $186.6714   $186.67   $186.65   $186.70  
  Purchase #2 $208.38   13.437%   $236.38   $236.38   $236.40   $236.40  
  Purchase #3 $44.55   4.765%   $46.6728   $46.67   $46.65   $46.70  
  Purchase #4 $184.42   12.564%   $207.5905   $207.59   $207.60   $207.60  
  Purchase #5 $45.28   6.366%   $48.1625   $48.16   $48.15   $48.20  
  Purchase #6 $84.93   5.107%   $89.2674   $89.27   $89.25   $89.30  
  Purchase #7 $207.25   7.371%   $222.5264   $222.53   $222.55   $222.50  
  7 purchase totals = $951.44       $1,037.2710   $1,037.27   $1,037.25   $1,037.40