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 $9.32   12.247%   $10.4614   $10.46   $10.45   $10.50  
  Purchase #2 $85.90   10.829%   $95.2021   $95.20   $95.20   $95.20  
  Purchase #3 $23.92   3.728%   $24.8117   $24.81   $24.80   $24.80  
  Purchase #4 $88.30   11.616%   $98.5569   $98.56   $98.55   $98.60  
  Purchase #5 $68.39   4.427%   $71.4176   $71.42   $71.40   $71.40  
  Purchase #6 $236.42   5.626%   $249.721   $249.72   $249.70   $249.70  
  Purchase #7 $197.76   5.368%   $208.3758   $208.38   $208.40   $208.40  
  7 purchase totals = $710.01       $758.5465   $758.55   $758.50   $758.60