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 $23.32   8.733%   $25.3565   $25.36   $25.35   $25.40  
  Purchase #2 $228.72   5.183%   $240.5746   $240.57   $240.55   $240.60  
  Purchase #3 $43.62   10.671%   $48.2747   $48.27   $48.25   $48.30  
  Purchase #4 $166.71   10.299%   $183.8795   $183.88   $183.90   $183.90  
  Purchase #5 $185.83   13.158%   $210.2815   $210.28   $210.30   $210.30  
  Purchase #6 $206.58   10.410%   $228.085   $228.09   $228.10   $228.10  
  Purchase #7 $176.76   5.708%   $186.8495   $186.85   $186.85   $186.80  
  7 purchase totals = $1,031.54       $1,123.3013   $1,123.30   $1,123.30   $1,123.40