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 $196.47   5.468%   $207.213   $207.21   $207.20   $207.20  
  Purchase #2 $51.28   8.131%   $55.4496   $55.45   $55.45   $55.40  
  Purchase #3 $162.28   10.295%   $178.9867   $178.99   $179.00   $179.00  
  Purchase #4 $108.65   4.417%   $113.4491   $113.45   $113.45   $113.40  
  Purchase #5 $223.61   11.184%   $248.6185   $248.62   $248.60   $248.60  
  Purchase #6 $110.28   3.374%   $114.0008   $114.00   $114.00   $114.00  
  Purchase #7 $94.87   4.531%   $99.1686   $99.17   $99.15   $99.20  
  7 purchase totals = $947.44       $1,016.8863   $1,016.89   $1,016.85   $1,016.80