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 $62.90   8.827%   $68.4522   $68.45   $68.45   $68.50  
  Purchase #2 $219.25   7.716%   $236.1673   $236.17   $236.15   $236.20  
  Purchase #3 $63.39   11.723%   $70.8212   $70.82   $70.80   $70.80  
  Purchase #4 $123.36   9.571%   $135.1668   $135.17   $135.15   $135.20  
  Purchase #5 $202.83   12.667%   $228.5225   $228.52   $228.50   $228.50  
  Purchase #6 $249.66   4.756%   $261.5338   $261.53   $261.55   $261.50  
  Purchase #7 $67.69   8.248%   $73.2731   $73.27   $73.25   $73.30  
  7 purchase totals = $989.08       $1,073.9369   $1,073.93   $1,073.85   $1,074.00