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 $182.79   5.828%   $193.443   $193.44   $193.45   $193.40  
  Purchase #2 $123.76   7.262%   $132.7475   $132.75   $132.75   $132.70  
  Purchase #3 $5.80   4.455%   $6.0584   $6.06   $6.05   $6.10  
  Purchase #4 $157.66   11.551%   $175.8713   $175.87   $175.85   $175.90  
  Purchase #5 $146.47   9.268%   $160.0448   $160.04   $160.05   $160.00  
  Purchase #6 $69.76   9.832%   $76.6188   $76.62   $76.60   $76.60  
  Purchase #7 $239.30   5.403%   $252.2294   $252.23   $252.25   $252.20  
  7 purchase totals = $925.54       $997.0132   $997.01   $997.00   $996.90