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 $43.26   8.490%   $46.9328   $46.93   $46.95   $46.90  
  Purchase #2 $214.53   6.347%   $228.1462   $228.15   $228.15   $228.10  
  Purchase #3 $103.84   11.412%   $115.6902   $115.69   $115.70   $115.70  
  Purchase #4 $130.42   4.102%   $135.7698   $135.77   $135.75   $135.80  
  Purchase #5 $87.69   6.812%   $93.6634   $93.66   $93.65   $93.70  
  Purchase #6 $67.89   5.448%   $71.5886   $71.59   $71.60   $71.60  
  Purchase #7 $171.41   13.858%   $195.164   $195.16   $195.15   $195.20  
  7 purchase totals = $819.04       $886.9550   $886.95   $886.95   $887.00