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 $24.88   4.835%   $26.0829   $26.08   $26.10   $26.10  
  Purchase #2 $199.87   8.366%   $216.5911   $216.59   $216.60   $216.60  
  Purchase #3 $192.30   3.776%   $199.5612   $199.56   $199.55   $199.60  
  Purchase #4 $58.39   5.528%   $61.6178   $61.62   $61.60   $61.60  
  Purchase #5 $162.67   9.692%   $178.436   $178.44   $178.45   $178.40  
  Purchase #6 $212.63   7.615%   $228.8218   $228.82   $228.80   $228.80  
  Purchase #7 $131.90   4.336%   $137.6192   $137.62   $137.60   $137.60  
  7 purchase totals = $982.64       $1,048.7300   $1,048.73   $1,048.70   $1,048.70