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 $184.37   6.527%   $196.4038   $196.40   $196.40   $196.40  
  Purchase #2 $177.26   3.635%   $183.7034   $183.70   $183.70   $183.70  
  Purchase #3 $15.76   8.270%   $17.0634   $17.06   $17.05   $17.10  
  Purchase #4 $102.86   5.215%   $108.2241   $108.22   $108.20   $108.20  
  Purchase #5 $207.78   7.170%   $222.6778   $222.68   $222.70   $222.70  
  Purchase #6 $49.30   13.418%   $55.9151   $55.92   $55.90   $55.90  
  Purchase #7 $227.42   11.548%   $253.6825   $253.68   $253.70   $253.70  
  7 purchase totals = $964.75       $1,037.6701   $1,037.66   $1,037.65   $1,037.70