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 $192.93   8.218%   $208.785   $208.79   $208.80   $208.80  
  Purchase #2 $250.37   4.474%   $261.5716   $261.57   $261.55   $261.60  
  Purchase #3 $5.79   11.287%   $6.4435   $6.44   $6.45   $6.40  
  Purchase #4 $69.38   4.599%   $72.5708   $72.57   $72.55   $72.60  
  Purchase #5 $196.71   7.782%   $212.018   $212.02   $212.00   $212.00  
  Purchase #6 $195.39   7.163%   $209.3858   $209.39   $209.40   $209.40  
  Purchase #7 $52.25   7.377%   $56.1045   $56.10   $56.10   $56.10  
  7 purchase totals = $962.82       $1,026.8792   $1,026.88   $1,026.85   $1,026.90