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	$217.58	9.799%	$238.9007	$238.90	$238.90	$238.90
Purchase #2	$108.84	5.235%	$114.5378	$114.54	$114.55	$114.50
Purchase #3	$241.59	5.233%	$254.2324	$254.23	$254.25	$254.20
Purchase #4	$10.76	10.784%	$11.9204	$11.92	$11.90	$11.90
Purchase #5	$51.63	7.794%	$55.654	$55.65	$55.65	$55.70
Purchase #6	$120.62	8.718%	$131.1357	$131.14	$131.15	$131.10
Purchase #7	$217.72	4.437%	$227.3802	$227.38	$227.40	$227.40
7 purchase totals =	$968.74		$1,033.7612	$1,033.76	$1,033.80	$1,033.70