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 $207.80   6.397%   $221.093   $221.09   $221.10   $221.10  
  Purchase #2 $216.81   8.751%   $235.783   $235.78   $235.80   $235.80  
  Purchase #3 $162.95   8.176%   $176.2728   $176.27   $176.25   $176.30  
  Purchase #4 $186.60   5.351%   $196.585   $196.59   $196.60   $196.60  
  Purchase #5 $144.92   5.364%   $152.6935   $152.69   $152.70   $152.70  
  Purchase #6 $55.33   13.344%   $62.7132   $62.71   $62.70   $62.70  
  Purchase #7 $201.63   8.147%   $218.0568   $218.06   $218.05   $218.10  
  7 purchase totals = $1,176.04       $1,263.1973   $1,263.19   $1,263.20   $1,263.30