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 $23.76   9.568%   $26.0334   $26.03   $26.05   $26.00  
  Purchase #2 $155.98   3.658%   $161.6857   $161.69   $161.70   $161.70  
  Purchase #3 $72.63   11.650%   $81.0914   $81.09   $81.10   $81.10  
  Purchase #4 $52.43   12.327%   $58.893   $58.89   $58.90   $58.90  
  Purchase #5 $124.95   7.235%   $133.9901   $133.99   $134.00   $134.00  
  Purchase #6 $110.78   5.737%   $117.1354   $117.14   $117.15   $117.10  
  Purchase #7 $227.84   13.368%   $258.2977   $258.30   $258.30   $258.30  
  7 purchase totals = $768.37       $837.1267   $837.13   $837.20   $837.10