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 $66.76   3.726%   $69.2475   $69.25   $69.25   $69.20  
  Purchase #2 $188.59   4.201%   $196.5127   $196.51   $196.50   $196.50  
  Purchase #3 $206.99   12.694%   $233.2653   $233.27   $233.25   $233.30  
  Purchase #4 $241.87   10.675%   $267.6896   $267.69   $267.70   $267.70  
  Purchase #5 $101.28   8.530%   $109.9192   $109.92   $109.90   $109.90  
  Purchase #6 $165.95   12.338%   $186.4249   $186.42   $186.40   $186.40  
  Purchase #7 $132.49   8.751%   $144.0842   $144.08   $144.10   $144.10  
  7 purchase totals = $1,103.93       $1,207.1434   $1,207.14   $1,207.10   $1,207.10