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 $108.46   5.691%   $114.6325   $114.63   $114.65   $114.60  
  Purchase #2 $228.65   4.713%   $239.4263   $239.43   $239.45   $239.40  
  Purchase #3 $66.74   12.804%   $75.2854   $75.29   $75.30   $75.30  
  Purchase #4 $55.31   3.815%   $57.4201   $57.42   $57.40   $57.40  
  Purchase #5 $155.53   12.777%   $175.4021   $175.40   $175.40   $175.40  
  Purchase #6 $130.60   8.728%   $141.9988   $142.00   $142.00   $142.00  
  Purchase #7 $19.74   9.721%   $21.6589   $21.66   $21.65   $21.70  
  7 purchase totals = $765.03       $825.8241   $825.83   $825.85   $825.80