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 $193.63   4.163%   $201.6908   $201.69   $201.70   $201.70  
  Purchase #2 $25.25   4.184%   $26.3065   $26.31   $26.30   $26.30  
  Purchase #3 $160.50   5.571%   $169.4415   $169.44   $169.45   $169.40  
  Purchase #4 $151.31   11.678%   $168.98   $168.98   $169.00   $169.00  
  Purchase #5 $26.54   3.170%   $27.3813   $27.38   $27.40   $27.40  
  Purchase #6 $187.64   4.175%   $195.474   $195.47   $195.45   $195.50  
  Purchase #7 $12.30   9.521%   $13.4711   $13.47   $13.45   $13.50  
  7 purchase totals = $757.17       $802.7452   $802.74   $802.75   $802.80