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 $76.83   11.873%   $85.952   $85.95   $85.95   $86.00  
  Purchase #2 $232.65   12.349%   $261.3799   $261.38   $261.40   $261.40  
  Purchase #3 $175.71   7.118%   $188.217   $188.22   $188.20   $188.20  
  Purchase #4 $150.83   8.266%   $163.2976   $163.30   $163.30   $163.30  
  Purchase #5 $190.61   6.688%   $203.358   $203.36   $203.35   $203.40  
  Purchase #6 $125.61   6.280%   $133.4983   $133.50   $133.50   $133.50  
  Purchase #7 $10.72   8.275%   $11.6071   $11.61   $11.60   $11.60  
  7 purchase totals = $962.96       $1,047.3099   $1,047.32   $1,047.30   $1,047.40