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 $110.31   3.676%   $114.365   $114.37   $114.35   $114.40  
  Purchase #2 $31.56   12.217%   $35.4157   $35.42   $35.40   $35.40  
  Purchase #3 $182.50   13.680%   $207.466   $207.47   $207.45   $207.50  
  Purchase #4 $248.82   5.187%   $261.7263   $261.73   $261.75   $261.70  
  Purchase #5 $44.55   4.377%   $46.5   $46.50   $46.50   $46.50  
  Purchase #6 $219.71   6.699%   $234.4284   $234.43   $234.45   $234.40  
  Purchase #7 $95.60   11.461%   $106.5567   $106.56   $106.55   $106.60  
  7 purchase totals = $933.05       $1,006.4581   $1,006.48   $1,006.45   $1,006.50