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 $60.80   4.775%   $63.7032   $63.70   $63.70   $63.70  
  Purchase #2 $239.91   11.327%   $267.0846   $267.08   $267.10   $267.10  
  Purchase #3 $152.95   7.140%   $163.8706   $163.87   $163.85   $163.90  
  Purchase #4 $208.79   12.252%   $234.371   $234.37   $234.35   $234.40  
  Purchase #5 $223.28   6.536%   $237.8736   $237.87   $237.85   $237.90  
  Purchase #6 $189.63   3.223%   $195.7418   $195.74   $195.75   $195.70  
  Purchase #7 $106.94   6.855%   $114.2707   $114.27   $114.25   $114.30  
  7 purchase totals = $1,182.30       $1,276.9155   $1,276.90   $1,276.85   $1,277.00