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 $86.93   10.574%   $96.122   $96.12   $96.10   $96.10  
  Purchase #2 $90.58   8.302%   $98.1   $98.10   $98.10   $98.10  
  Purchase #3 $82.46   5.282%   $86.8155   $86.82   $86.80   $86.80  
  Purchase #4 $244.55   10.688%   $270.6875   $270.69   $270.70   $270.70  
  Purchase #5 $79.36   8.576%   $86.1659   $86.17   $86.15   $86.20  
  Purchase #6 $42.43   9.203%   $46.3348   $46.33   $46.35   $46.30  
  Purchase #7 $176.77   13.554%   $200.7294   $200.73   $200.75   $200.70  
  7 purchase totals = $803.08       $884.9551   $884.96   $884.95   $884.90