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	$115.91	10.114%	$127.6331	$127.63	$127.65	$127.60
Purchase #2	$109.90	12.748%	$123.9101	$123.91	$123.90	$123.90
Purchase #3	$183.79	11.317%	$204.5895	$204.59	$204.60	$204.60
Purchase #4	$230.65	10.569%	$255.0274	$255.03	$255.05	$255.00
Purchase #5	$62.93	6.518%	$67.0318	$67.03	$67.05	$67.00
Purchase #6	$92.83	13.179%	$105.0641	$105.06	$105.05	$105.10
Purchase #7	$8.80	8.429%	$9.5418	$9.54	$9.55	$9.50
7 purchase totals =	$804.81		$892.7978	$892.79	$892.85	$892.70