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	$82.29	8.527%	$89.3069	$89.31	$89.30	$89.30
Purchase #2	$144.52	4.432%	$150.9251	$150.93	$150.95	$150.90
Purchase #3	$201.66	3.206%	$208.1252	$208.13	$208.15	$208.10
Purchase #4	$48.75	6.494%	$51.9158	$51.92	$51.90	$51.90
Purchase #5	$11.36	8.104%	$12.2806	$12.28	$12.30	$12.30
Purchase #6	$51.90	5.249%	$54.6242	$54.62	$54.60	$54.60
Purchase #7	$131.64	10.868%	$145.9466	$145.95	$145.95	$145.90
7 purchase totals =	$672.12		$713.1244	$713.14	$713.15	$713.00