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 $113.86   3.492%   $117.836   $117.84   $117.85   $117.80  
  Purchase #2 $164.86   5.569%   $174.0411   $174.04   $174.05   $174.00  
  Purchase #3 $101.29   6.158%   $107.5274   $107.53   $107.55   $107.50  
  Purchase #4 $57.72   5.833%   $61.0868   $61.09   $61.10   $61.10  
  Purchase #5 $89.51   4.132%   $93.2086   $93.21   $93.20   $93.20  
  Purchase #6 $197.93   12.271%   $222.218   $222.22   $222.20   $222.20  
  Purchase #7 $174.89   7.847%   $188.6136   $188.61   $188.60   $188.60  
  7 purchase totals = $900.06       $964.5315   $964.54   $964.55   $964.40