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 $161.47   9.471%   $176.7628   $176.76   $176.75   $176.80  
  Purchase #2 $70.47   4.556%   $73.6806   $73.68   $73.70   $73.70  
  Purchase #3 $223.88   4.645%   $234.2792   $234.28   $234.30   $234.30  
  Purchase #4 $237.88   10.686%   $263.2999   $263.30   $263.30   $263.30  
  Purchase #5 $89.69   10.212%   $98.8491   $98.85   $98.85   $98.80  
  Purchase #6 $228.79   12.611%   $257.6427   $257.64   $257.65   $257.60  
  Purchase #7 $95.25   8.760%   $103.5939   $103.59   $103.60   $103.60  
  7 purchase totals = $1,107.43       $1,208.1082   $1,208.10   $1,208.15   $1,208.10