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 $60.82   5.175%   $63.9674   $63.97   $63.95   $64.00  
  Purchase #2 $174.25   3.238%   $179.8922   $179.89   $179.90   $179.90  
  Purchase #3 $65.42   12.595%   $73.6596   $73.66   $73.65   $73.70  
  Purchase #4 $223.44   12.126%   $250.5343   $250.53   $250.55   $250.50  
  Purchase #5 $210.58   12.448%   $236.793   $236.79   $236.80   $236.80  
  Purchase #6 $126.42   8.543%   $137.2201   $137.22   $137.20   $137.20  
  Purchase #7 $22.42   13.183%   $25.3756   $25.38   $25.40   $25.40  
  7 purchase totals = $883.35       $967.4422   $967.44   $967.45   $967.50