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 $152.98   5.242%   $160.9992   $161.00   $161.00   $161.00  
  Purchase #2 $57.95   9.156%   $63.2559   $63.26   $63.25   $63.30  
  Purchase #3 $12.81   6.291%   $13.6159   $13.62   $13.60   $13.60  
  Purchase #4 $142.66   7.621%   $153.5321   $153.53   $153.55   $153.50  
  Purchase #5 $86.70   3.520%   $89.7518   $89.75   $89.75   $89.80  
  Purchase #6 $245.48   6.593%   $261.6645   $261.66   $261.65   $261.70  
  Purchase #7 $63.34   13.218%   $71.7123   $71.71   $71.70   $71.70  
  7 purchase totals = $761.92       $814.5317   $814.53   $814.50   $814.60