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 $67.95   8.246%   $73.5532   $73.55   $73.55   $73.60  
  Purchase #2 $195.30   13.380%   $221.4311   $221.43   $221.45   $221.40  
  Purchase #3 $111.34   3.776%   $115.5442   $115.54   $115.55   $115.50  
  Purchase #4 $70.63   12.179%   $79.232   $79.23   $79.25   $79.20  
  Purchase #5 $103.49   5.275%   $108.9491   $108.95   $108.95   $108.90  
  Purchase #6 $196.98   7.733%   $212.2125   $212.21   $212.20   $212.20  
  Purchase #7 $236.59   11.563%   $263.9469   $263.95   $263.95   $263.90  
  7 purchase totals = $982.28       $1,074.8690   $1,074.86   $1,074.90   $1,074.70