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	$38.57	11.608%	$43.0472	$43.05	$43.05	$43.00
Purchase #2	$179.84	9.253%	$196.4806	$196.48	$196.50	$196.50
Purchase #3	$174.93	8.301%	$189.4509	$189.45	$189.45	$189.50
Purchase #4	$160.60	9.539%	$175.9196	$175.92	$175.90	$175.90
Purchase #5	$16.58	6.509%	$17.6592	$17.66	$17.65	$17.70
Purchase #6	$238.61	8.502%	$258.8966	$258.90	$258.90	$258.90
Purchase #7	$204.50	12.519%	$230.1014	$230.10	$230.10	$230.10
7 purchase totals =	$1,013.63		$1,111.5555	$1,111.56	$1,111.55	$1,111.60