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 $24.61   5.730%   $26.0202   $26.02   $26.00   $26.00  
  Purchase #2 $145.47   13.779%   $165.5143   $165.51   $165.50   $165.50  
  Purchase #3 $21.41   10.650%   $23.6902   $23.69   $23.70   $23.70  
  Purchase #4 $191.30   6.775%   $204.2606   $204.26   $204.25   $204.30  
  Purchase #5 $142.62   5.658%   $150.6894   $150.69   $150.70   $150.70  
  Purchase #6 $123.65   12.504%   $139.1112   $139.11   $139.10   $139.10  
  Purchase #7 $137.74   6.270%   $146.3763   $146.38   $146.40   $146.40  
  7 purchase totals = $786.80       $855.6622   $855.66   $855.65   $855.70