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 $246.78   6.267%   $262.2457   $262.25   $262.25   $262.20  
  Purchase #2 $51.32   4.755%   $53.7603   $53.76   $53.75   $53.80  
  Purchase #3 $177.77   11.681%   $198.5353   $198.54   $198.55   $198.50  
  Purchase #4 $87.28   11.274%   $97.1199   $97.12   $97.10   $97.10  
  Purchase #5 $171.46   9.731%   $188.1448   $188.14   $188.15   $188.10  
  Purchase #6 $229.87   11.716%   $256.8016   $256.80   $256.80   $256.80  
  Purchase #7 $89.66   3.125%   $92.4619   $92.46   $92.45   $92.50  
  7 purchase totals = $1,054.14       $1,149.0695   $1,149.07   $1,149.05   $1,149.00