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 $92.76   3.136%   $95.669   $95.67   $95.65   $95.70  
  Purchase #2 $24.90   5.358%   $26.2341   $26.23   $26.25   $26.20  
  Purchase #3 $57.92   10.660%   $64.0943   $64.09   $64.10   $64.10  
  Purchase #4 $189.86   11.285%   $211.2857   $211.29   $211.30   $211.30  
  Purchase #5 $85.29   9.706%   $93.5682   $93.57   $93.55   $93.60  
  Purchase #6 $183.46   7.260%   $196.7792   $196.78   $196.80   $196.80  
  Purchase #7 $19.74   7.116%   $21.1447   $21.14   $21.15   $21.10  
  7 purchase totals = $653.93       $708.7752   $708.77   $708.80   $708.80