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 $41.84   12.215%   $46.9508   $46.95   $46.95   $47.00  
  Purchase #2 $240.34   4.304%   $250.6842   $250.68   $250.70   $250.70  
  Purchase #3 $186.26   8.212%   $201.5557   $201.56   $201.55   $201.60  
  Purchase #4 $137.47   7.587%   $147.8998   $147.90   $147.90   $147.90  
  Purchase #5 $59.33   3.314%   $61.2962   $61.30   $61.30   $61.30  
  Purchase #6 $216.62   10.690%   $239.7767   $239.78   $239.80   $239.80  
  Purchase #7 $26.83   9.633%   $29.4145   $29.41   $29.40   $29.40  
  7 purchase totals = $908.69       $977.5779   $977.58   $977.60   $977.70