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 $95.60   8.721%   $103.9373   $103.94   $103.95   $103.90  
  Purchase #2 $94.63   8.853%   $103.0076   $103.01   $103.00   $103.00  
  Purchase #3 $30.88   3.697%   $32.0216   $32.02   $32.00   $32.00  
  Purchase #4 $152.25   9.481%   $166.6848   $166.68   $166.70   $166.70  
  Purchase #5 $208.89   4.542%   $218.3778   $218.38   $218.40   $218.40  
  Purchase #6 $201.93   11.677%   $225.5094   $225.51   $225.50   $225.50  
  Purchase #7 $239.94   3.825%   $249.1177   $249.12   $249.10   $249.10  
  7 purchase totals = $1,024.12       $1,098.6562   $1,098.66   $1,098.65   $1,098.60