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	$156.29	11.693%	$174.565	$174.57	$174.55	$174.60
Purchase #2	$104.44	9.768%	$114.6417	$114.64	$114.65	$114.60
Purchase #3	$17.92	4.252%	$18.682	$18.68	$18.70	$18.70
Purchase #4	$236.25	12.851%	$266.6105	$266.61	$266.60	$266.60
Purchase #5	$69.76	12.434%	$78.434	$78.43	$78.45	$78.40
Purchase #6	$217.75	10.753%	$241.1647	$241.16	$241.15	$241.20
Purchase #7	$101.67	9.792%	$111.6255	$111.63	$111.65	$111.60
7 purchase totals =	$904.08		$1,005.7234	$1,005.72	$1,005.75	$1,005.70