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	$152.35	9.571%	$166.9314	$166.93	$166.95	$166.90
Purchase #2	$60.49	7.699%	$65.1471	$65.15	$65.15	$65.10
Purchase #3	$243.37	4.291%	$253.813	$253.81	$253.80	$253.80
Purchase #4	$21.57	9.388%	$23.595	$23.60	$23.60	$23.60
Purchase #5	$185.69	5.608%	$196.1035	$196.10	$196.10	$196.10
Purchase #6	$228.49	13.522%	$259.3864	$259.39	$259.40	$259.40
Purchase #7	$232.79	10.784%	$257.8941	$257.89	$257.90	$257.90
7 purchase totals =	$1,124.75		$1,222.8705	$1,222.87	$1,222.90	$1,222.80