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 $188.91   13.526%   $214.462   $214.46   $214.45   $214.50  
  Purchase #2 $124.26   7.831%   $133.9908   $133.99   $134.00   $134.00  
  Purchase #3 $56.71   4.173%   $59.0765   $59.08   $59.10   $59.10  
  Purchase #4 $52.83   8.333%   $57.2323   $57.23   $57.25   $57.20  
  Purchase #5 $201.69   12.192%   $226.28   $226.28   $226.30   $226.30  
  Purchase #6 $101.59   12.296%   $114.0815   $114.08   $114.10   $114.10  
  Purchase #7 $240.50   3.177%   $248.1407   $248.14   $248.15   $248.10  
  7 purchase totals = $966.49       $1,053.2638   $1,053.26   $1,053.35   $1,053.30