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 $164.95   10.361%   $182.0405   $182.04   $182.05   $182.00  
  Purchase #2 $220.59   12.822%   $248.874   $248.87   $248.85   $248.90  
  Purchase #3 $219.49   3.628%   $227.4531   $227.45   $227.45   $227.50  
  Purchase #4 $53.73   7.596%   $57.8113   $57.81   $57.80   $57.80  
  Purchase #5 $138.49   9.533%   $151.6923   $151.69   $151.70   $151.70  
  Purchase #6 $237.42   6.572%   $253.0232   $253.02   $253.00   $253.00  
  Purchase #7 $214.47   4.281%   $223.6515   $223.65   $223.65   $223.70  
  7 purchase totals = $1,249.14       $1,344.5459   $1,344.53   $1,344.50   $1,344.60