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 $176.67   5.680%   $186.7049   $186.70   $186.70   $186.70  
  Purchase #2 $164.93   11.337%   $183.6281   $183.63   $183.65   $183.60  
  Purchase #3 $217.47   3.111%   $224.2355   $224.24   $224.25   $224.20  
  Purchase #4 $74.91   10.318%   $82.6392   $82.64   $82.65   $82.60  
  Purchase #5 $143.87   4.535%   $150.3945   $150.39   $150.40   $150.40  
  Purchase #6 $157.99   13.314%   $179.0248   $179.02   $179.00   $179.00  
  Purchase #7 $83.67   8.619%   $90.8815   $90.88   $90.90   $90.90  
  7 purchase totals = $1,019.51       $1,097.5085   $1,097.50   $1,097.55   $1,097.40