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 $213.66   5.627%   $225.6826   $225.68   $225.70   $225.70  
  Purchase #2 $210.81   10.233%   $232.3822   $232.38   $232.40   $232.40  
  Purchase #3 $162.95   8.298%   $176.4716   $176.47   $176.45   $176.50  
  Purchase #4 $208.91   4.232%   $217.7511   $217.75   $217.75   $217.80  
  Purchase #5 $54.70   5.872%   $57.912   $57.91   $57.90   $57.90  
  Purchase #6 $170.90   3.806%   $177.4045   $177.40   $177.40   $177.40  
  Purchase #7 $207.61   4.219%   $216.3691   $216.37   $216.35   $216.40  
  7 purchase totals = $1,229.54       $1,303.9731   $1,303.96   $1,303.95   $1,304.10