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 $60.42   3.616%   $62.6048   $62.60   $62.60   $62.60  
  Purchase #2 $55.48   4.406%   $57.9244   $57.92   $57.90   $57.90  
  Purchase #3 $118.26   13.769%   $134.5432   $134.54   $134.55   $134.50  
  Purchase #4 $147.29   3.366%   $152.2478   $152.25   $152.25   $152.20  
  Purchase #5 $23.47   5.209%   $24.6926   $24.69   $24.70   $24.70  
  Purchase #6 $180.77   4.144%   $188.2611   $188.26   $188.25   $188.30  
  Purchase #7 $162.76   8.592%   $176.7443   $176.74   $176.75   $176.70  
  7 purchase totals = $748.45       $797.0182   $797.00   $797.00   $796.90