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 $227.57   7.216%   $243.9915   $243.99   $244.00   $244.00  
  Purchase #2 $142.41   5.190%   $149.8011   $149.80   $149.80   $149.80  
  Purchase #3 $66.63   8.709%   $72.4328   $72.43   $72.45   $72.40  
  Purchase #4 $201.68   3.393%   $208.523   $208.52   $208.50   $208.50  
  Purchase #5 $142.38   13.151%   $161.1044   $161.10   $161.10   $161.10  
  Purchase #6 $63.61   8.372%   $68.9354   $68.94   $68.95   $68.90  
  Purchase #7 $44.93   4.507%   $46.955   $46.96   $46.95   $47.00  
  7 purchase totals = $889.21       $951.7432   $951.74   $951.75   $951.70