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 $84.50   13.484%   $95.894   $95.89   $95.90   $95.90  
  Purchase #2 $248.91   4.780%   $260.8079   $260.81   $260.80   $260.80  
  Purchase #3 $28.91   4.619%   $30.2454   $30.25   $30.25   $30.20  
  Purchase #4 $239.31   5.510%   $252.496   $252.50   $252.50   $252.50  
  Purchase #5 $34.78   5.490%   $36.6894   $36.69   $36.70   $36.70  
  Purchase #6 $59.55   8.428%   $64.5689   $64.57   $64.55   $64.60  
  Purchase #7 $133.59   3.190%   $137.8515   $137.85   $137.85   $137.90  
  7 purchase totals = $829.55       $878.5531   $878.56   $878.55   $878.60