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 $161.65   8.360%   $175.1639   $175.16   $175.15   $175.20  
  Purchase #2 $177.27   7.292%   $190.1965   $190.20   $190.20   $190.20  
  Purchase #3 $61.60   3.135%   $63.5312   $63.53   $63.55   $63.50  
  Purchase #4 $239.54   3.819%   $248.688   $248.69   $248.70   $248.70  
  Purchase #5 $182.41   9.665%   $200.0399   $200.04   $200.05   $200.00  
  Purchase #6 $77.72   6.755%   $82.97   $82.97   $82.95   $83.00  
  Purchase #7 $194.68   3.570%   $201.6301   $201.63   $201.65   $201.60  
  7 purchase totals = $1,094.87       $1,162.2196   $1,162.22   $1,162.25   $1,162.20