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 $185.68   5.566%   $196.0149   $196.01   $196.00   $196.00  
  Purchase #2 $62.26   11.227%   $69.2499   $69.25   $69.25   $69.20  
  Purchase #3 $5.67   6.387%   $6.0321   $6.03   $6.05   $6.00  
  Purchase #4 $46.46   7.348%   $49.8739   $49.87   $49.85   $49.90  
  Purchase #5 $84.76   13.235%   $95.978   $95.98   $96.00   $96.00  
  Purchase #6 $198.53   7.102%   $212.6296   $212.63   $212.65   $212.60  
  Purchase #7 $245.33   4.280%   $255.8301   $255.83   $255.85   $255.80  
  7 purchase totals = $828.69       $885.6085   $885.60   $885.65   $885.50