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 $58.85   4.781%   $61.6636   $61.66   $61.65   $61.70  
  Purchase #2 $136.37   5.766%   $144.2331   $144.23   $144.25   $144.20  
  Purchase #3 $122.44   11.212%   $136.168   $136.17   $136.15   $136.20  
  Purchase #4 $95.64   3.583%   $99.0668   $99.07   $99.05   $99.10  
  Purchase #5 $63.74   4.407%   $66.549   $66.55   $66.55   $66.50  
  Purchase #6 $186.34   4.848%   $195.3738   $195.37   $195.35   $195.40  
  Purchase #7 $226.80   9.741%   $248.8926   $248.89   $248.90   $248.90  
  7 purchase totals = $890.18       $951.9469   $951.94   $951.90   $952.00