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 $239.50   9.618%   $262.5351   $262.54   $262.55   $262.50  
  Purchase #2 $233.49   8.157%   $252.5358   $252.54   $252.55   $252.50  
  Purchase #3 $49.86   4.759%   $52.2328   $52.23   $52.25   $52.20  
  Purchase #4 $201.34   3.238%   $207.8594   $207.86   $207.85   $207.90  
  Purchase #5 $226.72   7.280%   $243.2252   $243.23   $243.25   $243.20  
  Purchase #6 $80.64   5.582%   $85.1413   $85.14   $85.15   $85.10  
  Purchase #7 $147.42   7.636%   $158.677   $158.68   $158.70   $158.70  
  7 purchase totals = $1,178.97       $1,262.2066   $1,262.22   $1,262.30   $1,262.10