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 $233.43   5.174%   $245.5077   $245.51   $245.50   $245.50  
  Purchase #2 $50.98   13.720%   $57.9745   $57.97   $57.95   $58.00  
  Purchase #3 $37.73   13.352%   $42.7677   $42.77   $42.75   $42.80  
  Purchase #4 $175.39   4.656%   $183.5562   $183.56   $183.55   $183.60  
  Purchase #5 $233.66   11.701%   $261.0006   $261.00   $261.00   $261.00  
  Purchase #6 $29.58   7.555%   $31.8148   $31.81   $31.80   $31.80  
  Purchase #7 $203.61   3.447%   $210.6284   $210.63   $210.65   $210.60  
  7 purchase totals = $964.38       $1,033.2499   $1,033.25   $1,033.20   $1,033.30