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 $183.47   13.666%   $208.543   $208.54   $208.55   $208.50  
  Purchase #2 $87.71   8.452%   $95.1232   $95.12   $95.10   $95.10  
  Purchase #3 $61.56   5.630%   $65.0258   $65.03   $65.05   $65.00  
  Purchase #4 $166.45   10.296%   $183.5877   $183.59   $183.60   $183.60  
  Purchase #5 $186.25   5.383%   $196.2758   $196.28   $196.30   $196.30  
  Purchase #6 $234.40   11.515%   $261.3912   $261.39   $261.40   $261.40  
  Purchase #7 $110.56   8.585%   $120.0516   $120.05   $120.05   $120.10  
  7 purchase totals = $1,030.40       $1,129.9983   $1,130.00   $1,130.05   $1,130.00