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 $186.54   8.697%   $202.7634   $202.76   $202.75   $202.80  
  Purchase #2 $248.28   4.673%   $259.8821   $259.88   $259.90   $259.90  
  Purchase #3 $68.89   10.581%   $76.1793   $76.18   $76.20   $76.20  
  Purchase #4 $226.59   3.603%   $234.754   $234.75   $234.75   $234.80  
  Purchase #5 $25.69   8.195%   $27.7953   $27.80   $27.80   $27.80  
  Purchase #6 $193.85   11.274%   $215.7046   $215.70   $215.70   $215.70  
  Purchase #7 $84.59   13.291%   $95.8329   $95.83   $95.85   $95.80  
  7 purchase totals = $1,034.43       $1,112.9116   $1,112.90   $1,112.95   $1,113.00