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 $122.86   3.291%   $126.9033   $126.90   $126.90   $126.90  
  Purchase #2 $148.30   10.840%   $164.3757   $164.38   $164.40   $164.40  
  Purchase #3 $77.33   11.311%   $86.0768   $86.08   $86.10   $86.10  
  Purchase #4 $184.28   9.563%   $201.9027   $201.90   $201.90   $201.90  
  Purchase #5 $144.55   13.112%   $163.5034   $163.50   $163.50   $163.50  
  Purchase #6 $205.63   6.853%   $219.7218   $219.72   $219.70   $219.70  
  Purchase #7 $56.68   7.687%   $61.037   $61.04   $61.05   $61.00  
  7 purchase totals = $939.63       $1,023.5207   $1,023.52   $1,023.55   $1,023.50