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	$159.91	13.542%	$181.565	$181.57	$181.55	$181.60
Purchase #2	$205.90	11.674%	$229.9368	$229.94	$229.95	$229.90
Purchase #3	$172.89	3.621%	$179.1503	$179.15	$179.15	$179.20
Purchase #4	$108.43	10.141%	$119.4259	$119.43	$119.45	$119.40
Purchase #5	$235.97	8.408%	$255.8104	$255.81	$255.80	$255.80
Purchase #6	$46.87	4.687%	$49.0668	$49.07	$49.05	$49.10
Purchase #7	$160.73	12.835%	$181.3597	$181.36	$181.35	$181.40
7 purchase totals =	$1,090.70		$1,196.3149	$1,196.33	$1,196.30	$1,196.40