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 $87.62   8.833%   $95.3595   $95.36   $95.35   $95.40  
  Purchase #2 $88.79   7.684%   $95.6126   $95.61   $95.60   $95.60  
  Purchase #3 $205.40   11.300%   $228.6102   $228.61   $228.60   $228.60  
  Purchase #4 $237.99   4.870%   $249.5801   $249.58   $249.60   $249.60  
  Purchase #5 $115.39   9.853%   $126.7594   $126.76   $126.75   $126.80  
  Purchase #6 $170.34   7.550%   $183.2007   $183.20   $183.20   $183.20  
  Purchase #7 $42.54   5.597%   $44.921   $44.92   $44.90   $44.90  
  7 purchase totals = $948.07       $1,024.0435   $1,024.04   $1,024.00   $1,024.10