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 $209.55   8.660%   $227.697   $227.70   $227.70   $227.70  
  Purchase #2 $198.98   8.786%   $216.4624   $216.46   $216.45   $216.50  
  Purchase #3 $187.63   8.475%   $203.5316   $203.53   $203.55   $203.50  
  Purchase #4 $237.49   8.346%   $257.3109   $257.31   $257.30   $257.30  
  Purchase #5 $226.68   13.665%   $257.6558   $257.66   $257.65   $257.70  
  Purchase #6 $235.69   7.458%   $253.2678   $253.27   $253.25   $253.30  
  Purchase #7 $64.55   9.580%   $70.7339   $70.73   $70.75   $70.70  
  7 purchase totals = $1,360.57       $1,486.6594   $1,486.66   $1,486.65   $1,486.70