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 $105.67   12.660%   $119.0478   $119.05   $119.05   $119.00  
  Purchase #2 $62.32   11.165%   $69.278   $69.28   $69.30   $69.30  
  Purchase #3 $224.87   5.254%   $236.6847   $236.68   $236.70   $236.70  
  Purchase #4 $215.90   10.345%   $238.2349   $238.23   $238.25   $238.20  
  Purchase #5 $38.86   11.234%   $43.2255   $43.23   $43.25   $43.20  
  Purchase #6 $236.28   12.869%   $266.6869   $266.69   $266.70   $266.70  
  Purchase #7 $175.93   5.851%   $186.2237   $186.22   $186.20   $186.20  
  7 purchase totals = $1,059.83       $1,159.3815   $1,159.38   $1,159.45   $1,159.30