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 $86.77   9.118%   $94.6817   $94.68   $94.70   $94.70  
  Purchase #2 $128.62   5.788%   $136.0645   $136.06   $136.05   $136.10  
  Purchase #3 $220.72   5.555%   $232.981   $232.98   $233.00   $233.00  
  Purchase #4 $182.84   11.402%   $203.6874   $203.69   $203.70   $203.70  
  Purchase #5 $99.54   13.795%   $113.2715   $113.27   $113.25   $113.30  
  Purchase #6 $222.34   4.662%   $232.7055   $232.71   $232.70   $232.70  
  Purchase #7 $192.68   5.611%   $203.4913   $203.49   $203.50   $203.50  
  7 purchase totals = $1,133.51       $1,216.8829   $1,216.88   $1,216.90   $1,217.00