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 $177.81   8.824%   $193.5   $193.50   $193.50   $193.50  
  Purchase #2 $186.64   13.393%   $211.6367   $211.64   $211.65   $211.60  
  Purchase #3 $151.83   3.768%   $157.551   $157.55   $157.55   $157.60  
  Purchase #4 $237.46   8.647%   $257.9932   $257.99   $258.00   $258.00  
  Purchase #5 $20.74   6.605%   $22.1099   $22.11   $22.10   $22.10  
  Purchase #6 $47.66   12.265%   $53.5055   $53.51   $53.50   $53.50  
  Purchase #7 $210.71   9.123%   $229.9331   $229.93   $229.95   $229.90  
  7 purchase totals = $1,032.85       $1,126.2294   $1,126.23   $1,126.25   $1,126.20