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	$126.78	13.152%	$143.4541	$143.45	$143.45	$143.50
Purchase #2	$231.72	4.543%	$242.247	$242.25	$242.25	$242.20
Purchase #3	$11.99	4.164%	$12.4893	$12.49	$12.50	$12.50
Purchase #4	$99.32	12.688%	$111.9217	$111.92	$111.90	$111.90
Purchase #5	$178.83	3.730%	$185.5004	$185.50	$185.50	$185.50
Purchase #6	$154.26	9.380%	$168.7296	$168.73	$168.75	$168.70
Purchase #7	$165.35	4.267%	$172.4055	$172.41	$172.40	$172.40
7 purchase totals =	$968.25		$1,036.7476	$1,036.75	$1,036.75	$1,036.70