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 $216.38   13.224%   $244.9941   $244.99   $245.00   $245.00  
  Purchase #2 $99.57   11.698%   $111.2177   $111.22   $111.20   $111.20  
  Purchase #3 $73.55   13.716%   $83.6381   $83.64   $83.65   $83.60  
  Purchase #4 $65.62   10.333%   $72.4005   $72.40   $72.40   $72.40  
  Purchase #5 $57.55   8.129%   $62.2282   $62.23   $62.25   $62.20  
  Purchase #6 $168.44   5.533%   $177.7598   $177.76   $177.75   $177.80  
  Purchase #7 $248.93   13.190%   $281.7639   $281.76   $281.75   $281.80  
  7 purchase totals = $930.04       $1,034.0023   $1,034.00   $1,034.00   $1,034.00