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 $85.88   10.664%   $95.0382   $95.04   $95.05   $95.00  
  Purchase #2 $35.97   3.310%   $37.1606   $37.16   $37.15   $37.20  
  Purchase #3 $233.51   7.480%   $250.9765   $250.98   $251.00   $251.00  
  Purchase #4 $103.78   10.116%   $114.2784   $114.28   $114.30   $114.30  
  Purchase #5 $232.35   5.732%   $245.6683   $245.67   $245.65   $245.70  
  Purchase #6 $86.28   13.613%   $98.0253   $98.03   $98.05   $98.00  
  Purchase #7 $18.53   3.713%   $19.218   $19.22   $19.20   $19.20  
  7 purchase totals = $796.30       $860.3653   $860.38   $860.40   $860.40