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 $161.68   8.630%   $175.633   $175.63   $175.65   $175.60  
  Purchase #2 $93.49   3.671%   $96.922   $96.92   $96.90   $96.90  
  Purchase #3 $66.76   7.199%   $71.5661   $71.57   $71.55   $71.60  
  Purchase #4 $89.85   13.193%   $101.7039   $101.70   $101.70   $101.70  
  Purchase #5 $186.37   11.733%   $208.2368   $208.24   $208.25   $208.20  
  Purchase #6 $154.83   13.380%   $175.5463   $175.55   $175.55   $175.50  
  Purchase #7 $124.90   6.759%   $133.342   $133.34   $133.35   $133.30  
  7 purchase totals = $877.88       $962.9501   $962.95   $962.95   $962.80