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 $63.76   8.757%   $69.3435   $69.34   $69.35   $69.30  
  Purchase #2 $161.31   10.117%   $177.6297   $177.63   $177.65   $177.60  
  Purchase #3 $12.66   12.535%   $14.2469   $14.25   $14.25   $14.20  
  Purchase #4 $162.30   5.213%   $170.7607   $170.76   $170.75   $170.80  
  Purchase #5 $24.25   7.525%   $26.0748   $26.07   $26.05   $26.10  
  Purchase #6 $88.75   3.435%   $91.7986   $91.80   $91.80   $91.80  
  Purchase #7 $167.41   4.227%   $174.4864   $174.49   $174.50   $174.50  
  7 purchase totals = $680.44       $724.3406   $724.34   $724.35   $724.30