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 $55.72   11.182%   $61.9506   $61.95   $61.95   $62.00  
  Purchase #2 $93.93   3.300%   $97.0297   $97.03   $97.05   $97.00  
  Purchase #3 $226.64   11.702%   $253.1614   $253.16   $253.15   $253.20  
  Purchase #4 $95.44   3.601%   $98.8768   $98.88   $98.90   $98.90  
  Purchase #5 $84.99   5.714%   $89.8463   $89.85   $89.85   $89.80  
  Purchase #6 $208.94   10.452%   $230.7784   $230.78   $230.80   $230.80  
  Purchase #7 $151.46   7.781%   $163.2451   $163.25   $163.25   $163.20  
  7 purchase totals = $917.12       $994.8883   $994.90   $994.95   $994.90