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 $23.66   10.393%   $26.119   $26.12   $26.10   $26.10  
  Purchase #2 $40.65   11.813%   $45.452   $45.45   $45.45   $45.50  
  Purchase #3 $246.48   4.671%   $257.9931   $257.99   $258.00   $258.00  
  Purchase #4 $222.94   8.123%   $241.0494   $241.05   $241.05   $241.00  
  Purchase #5 $124.34   10.490%   $137.3833   $137.38   $137.40   $137.40  
  Purchase #6 $67.27   8.516%   $72.9987   $73.00   $73.00   $73.00  
  Purchase #7 $236.38   6.871%   $252.6217   $252.62   $252.60   $252.60  
  7 purchase totals = $961.72       $1,033.6172   $1,033.61   $1,033.60   $1,033.60