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 $207.49   8.627%   $225.3902   $225.39   $225.40   $225.40  
  Purchase #2 $164.37   12.777%   $185.3716   $185.37   $185.35   $185.40  
  Purchase #3 $12.97   13.855%   $14.767   $14.77   $14.75   $14.80  
  Purchase #4 $119.45   12.762%   $134.6942   $134.69   $134.70   $134.70  
  Purchase #5 $177.35   13.401%   $201.1167   $201.12   $201.10   $201.10  
  Purchase #6 $198.52   8.417%   $215.2294   $215.23   $215.25   $215.20  
  Purchase #7 $107.83   10.275%   $118.9095   $118.91   $118.90   $118.90  
  7 purchase totals = $987.98       $1,095.4786   $1,095.48   $1,095.45   $1,095.50