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 $173.76   13.344%   $196.9465   $196.95   $196.95   $196.90  
  Purchase #2 $214.60   11.195%   $238.6245   $238.62   $238.60   $238.60  
  Purchase #3 $222.85   10.334%   $245.8793   $245.88   $245.90   $245.90  
  Purchase #4 $229.65   8.750%   $249.7444   $249.74   $249.75   $249.70  
  Purchase #5 $15.74   8.564%   $17.088   $17.09   $17.10   $17.10  
  Purchase #6 $234.33   5.520%   $247.265   $247.27   $247.25   $247.30  
  Purchase #7 $242.70   5.285%   $255.5267   $255.53   $255.55   $255.50  
  7 purchase totals = $1,333.63       $1,451.0744   $1,451.08   $1,451.10   $1,451.00