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 $213.86   8.811%   $232.7032   $232.70   $232.70   $232.70  
  Purchase #2 $65.32   4.353%   $68.1634   $68.16   $68.15   $68.20  
  Purchase #3 $97.26   13.549%   $110.4378   $110.44   $110.45   $110.40  
  Purchase #4 $199.86   7.721%   $215.2912   $215.29   $215.30   $215.30  
  Purchase #5 $250.36   4.301%   $261.128   $261.13   $261.15   $261.10  
  Purchase #6 $47.86   13.154%   $54.1555   $54.16   $54.15   $54.20  
  Purchase #7 $175.58   8.407%   $190.341   $190.34   $190.35   $190.30  
  7 purchase totals = $1,050.10       $1,132.2201   $1,132.22   $1,132.25   $1,132.20