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	$150.81	4.660%	$157.8377	$157.84	$157.85	$157.80
Purchase #2	$159.32	11.250%	$177.2435	$177.24	$177.25	$177.20
Purchase #3	$156.48	10.268%	$172.5474	$172.55	$172.55	$172.50
Purchase #4	$174.44	12.683%	$196.5642	$196.56	$196.55	$196.60
Purchase #5	$50.81	11.120%	$56.4601	$56.46	$56.45	$56.50
Purchase #6	$153.42	7.857%	$165.4742	$165.47	$165.45	$165.50
Purchase #7	$176.69	3.823%	$183.4449	$183.44	$183.45	$183.40
7 purchase totals =	$1,021.97		$1,109.5720	$1,109.56	$1,109.55	$1,109.50