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 $207.42   13.591%   $235.6105   $235.61   $235.60   $235.60  
  Purchase #2 $232.89   3.839%   $241.8306   $241.83   $241.85   $241.80  
  Purchase #3 $107.63   13.325%   $121.9717   $121.97   $121.95   $122.00  
  Purchase #4 $133.45   7.460%   $143.4054   $143.41   $143.40   $143.40  
  Purchase #5 $151.55   6.191%   $160.9325   $160.93   $160.95   $160.90  
  Purchase #6 $188.50   10.638%   $208.5526   $208.55   $208.55   $208.60  
  Purchase #7 $76.27   7.750%   $82.1809   $82.18   $82.20   $82.20  
  7 purchase totals = $1,097.71       $1,194.4842   $1,194.48   $1,194.50   $1,194.50