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 $114.80   9.833%   $126.0883   $126.09   $126.10   $126.10  
  Purchase #2 $105.79   6.219%   $112.3691   $112.37   $112.35   $112.40  
  Purchase #3 $44.87   3.713%   $46.536   $46.54   $46.55   $46.50  
  Purchase #4 $164.48   11.614%   $183.5827   $183.58   $183.60   $183.60  
  Purchase #5 $96.45   12.190%   $108.2073   $108.21   $108.20   $108.20  
  Purchase #6 $228.64   9.275%   $249.8464   $249.85   $249.85   $249.80  
  Purchase #7 $159.31   12.382%   $179.0358   $179.04   $179.05   $179.00  
  7 purchase totals = $914.34       $1,005.6656   $1,005.68   $1,005.70   $1,005.60