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 $182.80   7.230%   $196.0164   $196.02   $196.00   $196.00  
  Purchase #2 $157.81   11.206%   $175.4942   $175.49   $175.50   $175.50  
  Purchase #3 $215.82   4.771%   $226.1168   $226.12   $226.10   $226.10  
  Purchase #4 $69.97   4.423%   $73.0648   $73.06   $73.05   $73.10  
  Purchase #5 $42.26   4.117%   $43.9998   $44.00   $44.00   $44.00  
  Purchase #6 $120.70   8.730%   $131.2371   $131.24   $131.25   $131.20  
  Purchase #7 $207.46   7.247%   $222.4946   $222.49   $222.50   $222.50  
  7 purchase totals = $996.82       $1,068.4237   $1,068.42   $1,068.40   $1,068.40