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 $44.83   3.644%   $46.4636   $46.46   $46.45   $46.50  
  Purchase #2 $249.96   3.595%   $258.9461   $258.95   $258.95   $258.90  
  Purchase #3 $177.73   11.447%   $198.0748   $198.07   $198.05   $198.10  
  Purchase #4 $109.95   5.520%   $116.0192   $116.02   $116.00   $116.00  
  Purchase #5 $179.25   12.379%   $201.4394   $201.44   $201.45   $201.40  
  Purchase #6 $100.90   6.673%   $107.6331   $107.63   $107.65   $107.60  
  Purchase #7 $220.63   5.570%   $232.9191   $232.92   $232.90   $232.90  
  7 purchase totals = $1,083.25       $1,161.4953   $1,161.49   $1,161.45   $1,161.40