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	$29.90	11.113%	$33.2228	$33.22	$33.20	$33.20
Purchase #2	$41.91	3.305%	$43.2951	$43.30	$43.30	$43.30
Purchase #3	$30.86	8.247%	$33.405	$33.41	$33.40	$33.40
Purchase #4	$59.45	6.174%	$63.1204	$63.12	$63.10	$63.10
Purchase #5	$7.90	8.731%	$8.5897	$8.59	$8.60	$8.60
Purchase #6	$100.81	10.835%	$111.7328	$111.73	$111.75	$111.70
Purchase #7	$250.92	9.842%	$275.6155	$275.62	$275.60	$275.60
7 purchase totals =	$521.75		$568.9813	$568.99	$568.95	$568.90