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 $214.42   9.601%   $235.0065   $235.01   $235.00   $235.00  
  Purchase #2 $30.32   10.372%   $33.4648   $33.46   $33.45   $33.50  
  Purchase #3 $153.62   6.727%   $163.954   $163.95   $163.95   $164.00  
  Purchase #4 $30.42   7.847%   $32.8071   $32.81   $32.80   $32.80  
  Purchase #5 $163.26   9.744%   $179.1681   $179.17   $179.15   $179.20  
  Purchase #6 $53.91   9.866%   $59.2288   $59.23   $59.25   $59.20  
  Purchase #7 $201.44   5.832%   $213.188   $213.19   $213.20   $213.20  
  7 purchase totals = $847.39       $916.8173   $916.82   $916.80   $916.90