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 $57.76   7.814%   $62.2734   $62.27   $62.25   $62.30  
  Purchase #2 $241.41   7.845%   $260.3486   $260.35   $260.35   $260.30  
  Purchase #3 $169.78   5.283%   $178.7495   $178.75   $178.75   $178.70  
  Purchase #4 $219.64   13.536%   $249.3705   $249.37   $249.35   $249.40  
  Purchase #5 $117.48   4.597%   $122.8806   $122.88   $122.90   $122.90  
  Purchase #6 $98.58   13.420%   $111.8094   $111.81   $111.80   $111.80  
  Purchase #7 $77.93   4.713%   $81.6028   $81.60   $81.60   $81.60  
  7 purchase totals = $982.58       $1,067.0348   $1,067.03   $1,067.00   $1,067.00