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 $53.26   5.798%   $56.348   $56.35   $56.35   $56.30  
  Purchase #2 $249.60   8.727%   $271.3826   $271.38   $271.40   $271.40  
  Purchase #3 $216.32   9.175%   $236.1674   $236.17   $236.15   $236.20  
  Purchase #4 $70.39   8.313%   $76.2415   $76.24   $76.25   $76.20  
  Purchase #5 $151.36   10.841%   $167.7689   $167.77   $167.75   $167.80  
  Purchase #6 $105.46   13.728%   $119.9375   $119.94   $119.95   $119.90  
  Purchase #7 $130.76   13.383%   $148.2596   $148.26   $148.25   $148.30  
  7 purchase totals = $977.15       $1,076.1055   $1,076.11   $1,076.10   $1,076.10