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 $200.68   3.654%   $208.0128   $208.01   $208.00   $208.00  
  Purchase #2 $226.65   12.684%   $255.3983   $255.40   $255.40   $255.40  
  Purchase #3 $157.42   8.390%   $170.6275   $170.63   $170.65   $170.60  
  Purchase #4 $194.25   3.779%   $201.5907   $201.59   $201.60   $201.60  
  Purchase #5 $234.81   11.402%   $261.583   $261.58   $261.60   $261.60  
  Purchase #6 $186.31   12.488%   $209.5764   $209.58   $209.60   $209.60  
  Purchase #7 $110.30   8.299%   $119.4538   $119.45   $119.45   $119.50  
  7 purchase totals = $1,310.42       $1,426.2425   $1,426.24   $1,426.30   $1,426.30