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 $41.89   11.260%   $46.6068   $46.61   $46.60   $46.60  
  Purchase #2 $226.43   4.111%   $235.7385   $235.74   $235.75   $235.70  
  Purchase #3 $80.97   8.599%   $87.9326   $87.93   $87.95   $87.90  
  Purchase #4 $192.56   7.872%   $207.7183   $207.72   $207.70   $207.70  
  Purchase #5 $61.27   9.803%   $67.2763   $67.28   $67.30   $67.30  
  Purchase #6 $27.54   11.447%   $30.6925   $30.69   $30.70   $30.70  
  Purchase #7 $199.41   13.212%   $225.756   $225.76   $225.75   $225.80  
  7 purchase totals = $830.07       $901.7210   $901.73   $901.75   $901.70