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 $62.37   4.464%   $65.1542   $65.15   $65.15   $65.20  
  Purchase #2 $239.98   4.164%   $249.9728   $249.97   $249.95   $250.00  
  Purchase #3 $224.38   3.519%   $232.2759   $232.28   $232.30   $232.30  
  Purchase #4 $137.87   12.393%   $154.9562   $154.96   $154.95   $155.00  
  Purchase #5 $137.67   9.376%   $150.5779   $150.58   $150.60   $150.60  
  Purchase #6 $54.51   5.499%   $57.5075   $57.51   $57.50   $57.50  
  Purchase #7 $178.76   9.230%   $195.2595   $195.26   $195.25   $195.30  
  7 purchase totals = $1,035.54       $1,105.7040   $1,105.71   $1,105.70   $1,105.90