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 $24.56   5.837%   $25.9936   $25.99   $26.00   $26.00  
  Purchase #2 $124.97   13.466%   $141.7985   $141.80   $141.80   $141.80  
  Purchase #3 $190.46   7.842%   $205.3959   $205.40   $205.40   $205.40  
  Purchase #4 $184.38   4.708%   $193.0606   $193.06   $193.05   $193.10  
  Purchase #5 $55.91   4.646%   $58.5076   $58.51   $58.50   $58.50  
  Purchase #6 $82.36   9.552%   $90.227   $90.23   $90.25   $90.20  
  Purchase #7 $141.65   7.356%   $152.0698   $152.07   $152.05   $152.10  
  7 purchase totals = $804.29       $867.0530   $867.06   $867.05   $867.10