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 $246.86   5.726%   $260.9952   $261.00   $261.00   $261.00  
  Purchase #2 $44.29   6.647%   $47.234   $47.23   $47.25   $47.20  
  Purchase #3 $181.49   6.108%   $192.5754   $192.58   $192.60   $192.60  
  Purchase #4 $58.74   3.802%   $60.9733   $60.97   $60.95   $61.00  
  Purchase #5 $207.46   9.529%   $227.2289   $227.23   $227.25   $227.20  
  Purchase #6 $58.62   6.726%   $62.5628   $62.56   $62.55   $62.60  
  Purchase #7 $247.58   3.421%   $256.0497   $256.05   $256.05   $256.00  
  7 purchase totals = $1,045.04       $1,107.6193   $1,107.62   $1,107.65   $1,107.60