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 $134.81   12.724%   $151.9632   $151.96   $151.95   $152.00  
  Purchase #2 $188.29   4.467%   $196.7009   $196.70   $196.70   $196.70  
  Purchase #3 $42.81   9.329%   $46.8037   $46.80   $46.80   $46.80  
  Purchase #4 $214.91   4.681%   $224.9699   $224.97   $224.95   $225.00  
  Purchase #5 $124.97   11.128%   $138.8767   $138.88   $138.90   $138.90  
  Purchase #6 $203.68   11.169%   $226.429   $226.43   $226.45   $226.40  
  Purchase #7 $164.62   11.468%   $183.4986   $183.50   $183.50   $183.50  
  7 purchase totals = $1,074.09       $1,169.2420   $1,169.24   $1,169.25   $1,169.30