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 $73.44   3.326%   $75.8826   $75.88   $75.90   $75.90  
  Purchase #2 $114.94   3.576%   $119.0503   $119.05   $119.05   $119.10  
  Purchase #3 $199.35   3.557%   $206.4409   $206.44   $206.45   $206.40  
  Purchase #4 $138.81   5.284%   $146.1447   $146.14   $146.15   $146.10  
  Purchase #5 $83.78   12.837%   $94.5348   $94.53   $94.55   $94.50  
  Purchase #6 $200.97   13.848%   $228.8003   $228.80   $228.80   $228.80  
  Purchase #7 $130.67   3.630%   $135.4133   $135.41   $135.40   $135.40  
  7 purchase totals = $941.96       $1,006.2669   $1,006.25   $1,006.30   $1,006.20