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	$157.38	13.509%	$178.6405	$178.64	$178.65	$178.60
Purchase #2	$118.59	7.820%	$127.8637	$127.86	$127.85	$127.90
Purchase #3	$33.94	13.622%	$38.5633	$38.56	$38.55	$38.60
Purchase #4	$139.27	10.791%	$154.2986	$154.30	$154.30	$154.30
Purchase #5	$46.29	13.716%	$52.6391	$52.64	$52.65	$52.60
Purchase #6	$12.47	13.439%	$14.1458	$14.15	$14.15	$14.10
Purchase #7	$212.79	4.711%	$222.8145	$222.81	$222.80	$222.80
7 purchase totals =	$720.73		$788.9655	$788.96	$788.95	$788.90