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	$38.70	12.660%	$43.5994	$43.60	$43.60	$43.60
Purchase #2	$87.38	6.115%	$92.7233	$92.72	$92.70	$92.70
Purchase #3	$114.44	6.742%	$122.1555	$122.16	$122.15	$122.20
Purchase #4	$230.76	3.178%	$238.0936	$238.09	$238.10	$238.10
Purchase #5	$117.57	8.496%	$127.5587	$127.56	$127.55	$127.60
Purchase #6	$126.49	12.409%	$142.1861	$142.19	$142.20	$142.20
Purchase #7	$54.74	8.359%	$59.3157	$59.32	$59.30	$59.30
7 purchase totals =	$770.08		$825.6323	$825.64	$825.60	$825.70