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	$209.28	4.430%	$218.5511	$218.55	$218.55	$218.60
Purchase #2	$139.30	5.452%	$146.8946	$146.89	$146.90	$146.90
Purchase #3	$12.81	5.363%	$13.497	$13.50	$13.50	$13.50
Purchase #4	$127.54	11.839%	$142.6395	$142.64	$142.65	$142.60
Purchase #5	$217.77	9.537%	$238.5387	$238.54	$238.55	$238.50
Purchase #6	$7.81	11.211%	$8.6856	$8.69	$8.70	$8.70
Purchase #7	$243.72	6.533%	$259.6422	$259.64	$259.65	$259.60
7 purchase totals =	$958.23		$1,028.4487	$1,028.45	$1,028.50	$1,028.40