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	$39.70	13.615%	$45.1052	$45.11	$45.10	$45.10
Purchase #2	$118.58	6.550%	$126.347	$126.35	$126.35	$126.30
Purchase #3	$176.52	5.278%	$185.8367	$185.84	$185.85	$185.80
Purchase #4	$23.47	3.611%	$24.3175	$24.32	$24.30	$24.30
Purchase #5	$45.89	11.776%	$51.294	$51.29	$51.30	$51.30
Purchase #6	$122.79	3.688%	$127.3185	$127.32	$127.30	$127.30
Purchase #7	$151.55	6.182%	$160.9188	$160.92	$160.90	$160.90
7 purchase totals =	$678.50		$721.1377	$721.15	$721.10	$721.00