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 $178.94   10.464%   $197.6643   $197.66   $197.65   $197.70  
  Purchase #2 $249.77   4.864%   $261.9188   $261.92   $261.90   $261.90  
  Purchase #3 $81.77   4.710%   $85.6214   $85.62   $85.60   $85.60  
  Purchase #4 $56.37   8.726%   $61.2888   $61.29   $61.30   $61.30  
  Purchase #5 $213.98   3.815%   $222.1433   $222.14   $222.15   $222.10  
  Purchase #6 $198.78   3.481%   $205.6995   $205.70   $205.70   $205.70  
  Purchase #7 $181.45   9.421%   $198.5444   $198.54   $198.55   $198.50  
  7 purchase totals = $1,161.06       $1,232.8805   $1,232.87   $1,232.85   $1,232.80