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 $212.79   11.681%   $237.646   $237.65   $237.65   $237.60  
  Purchase #2 $175.59   9.560%   $192.3764   $192.38   $192.40   $192.40  
  Purchase #3 $122.55   8.560%   $133.0403   $133.04   $133.05   $133.00  
  Purchase #4 $158.78   4.804%   $166.4078   $166.41   $166.40   $166.40  
  Purchase #5 $74.25   9.369%   $81.2065   $81.21   $81.20   $81.20  
  Purchase #6 $192.61   12.837%   $217.3353   $217.34   $217.35   $217.30  
  Purchase #7 $182.92   13.530%   $207.6691   $207.67   $207.65   $207.70  
  7 purchase totals = $1,119.49       $1,235.6814   $1,235.70   $1,235.70   $1,235.60