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 $102.38   11.493%   $114.1465   $114.15   $114.15   $114.10  
  Purchase #2 $206.56   3.221%   $213.2133   $213.21   $213.20   $213.20  
  Purchase #3 $30.80   5.515%   $32.4986   $32.50   $32.50   $32.50  
  Purchase #4 $51.55   11.452%   $57.4535   $57.45   $57.45   $57.50  
  Purchase #5 $84.77   8.626%   $92.0823   $92.08   $92.10   $92.10  
  Purchase #6 $61.88   6.155%   $65.6887   $65.69   $65.70   $65.70  
  Purchase #7 $245.84   5.129%   $258.4491   $258.45   $258.45   $258.40  
  7 purchase totals = $783.78       $833.5320   $833.53   $833.55   $833.50