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 $103.77   10.145%   $114.2975   $114.30   $114.30   $114.30  
  Purchase #2 $48.69   4.231%   $50.7501   $50.75   $50.75   $50.80  
  Purchase #3 $69.69   12.122%   $78.1378   $78.14   $78.15   $78.10  
  Purchase #4 $232.60   8.324%   $251.9616   $251.96   $251.95   $252.00  
  Purchase #5 $17.46   12.182%   $19.587   $19.59   $19.60   $19.60  
  Purchase #6 $5.42   6.784%   $5.7877   $5.79   $5.80   $5.80  
  Purchase #7 $182.93   12.549%   $205.8859   $205.89   $205.90   $205.90  
  7 purchase totals = $660.56       $726.4076   $726.42   $726.45   $726.50