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 $202.42   5.783%   $214.1259   $214.13   $214.15   $214.10  
  Purchase #2 $196.29   3.255%   $202.6792   $202.68   $202.70   $202.70  
  Purchase #3 $52.42   13.459%   $59.4752   $59.48   $59.50   $59.50  
  Purchase #4 $160.49   9.841%   $176.2838   $176.28   $176.30   $176.30  
  Purchase #5 $230.33   13.473%   $261.3624   $261.36   $261.35   $261.40  
  Purchase #6 $218.72   11.812%   $244.5552   $244.56   $244.55   $244.60  
  Purchase #7 $182.79   13.870%   $208.143   $208.14   $208.15   $208.10  
  7 purchase totals = $1,243.46       $1,366.6247   $1,366.63   $1,366.70   $1,366.70