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 $67.41   12.836%   $76.0627   $76.06   $76.05   $76.10  
  Purchase #2 $33.70   4.685%   $35.2788   $35.28   $35.30   $35.30  
  Purchase #3 $188.43   12.843%   $212.6301   $212.63   $212.65   $212.60  
  Purchase #4 $174.59   9.338%   $190.8932   $190.89   $190.90   $190.90  
  Purchase #5 $224.31   11.599%   $250.3277   $250.33   $250.35   $250.30  
  Purchase #6 $170.67   13.577%   $193.8419   $193.84   $193.85   $193.80  
  Purchase #7 $32.39   9.699%   $35.5315   $35.53   $35.55   $35.50  
  7 purchase totals = $891.50       $994.5659   $994.56   $994.65   $994.50