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 $68.67   5.844%   $72.6831   $72.68   $72.70   $72.70  
  Purchase #2 $220.47   8.517%   $239.2474   $239.25   $239.25   $239.20  
  Purchase #3 $71.68   4.767%   $75.097   $75.10   $75.10   $75.10  
  Purchase #4 $45.50   9.406%   $49.7797   $49.78   $49.80   $49.80  
  Purchase #5 $59.74   7.382%   $64.15   $64.15   $64.15   $64.20  
  Purchase #6 $86.86   6.434%   $92.4486   $92.45   $92.45   $92.40  
  Purchase #7 $122.96   7.147%   $131.748   $131.75   $131.75   $131.70  
  7 purchase totals = $675.88       $725.1538   $725.16   $725.20   $725.10