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	$112.72	4.821%	$118.1542	$118.15	$118.15	$118.20
Purchase #2	$103.40	10.789%	$114.5558	$114.56	$114.55	$114.60
Purchase #3	$226.84	12.801%	$255.8778	$255.88	$255.90	$255.90
Purchase #4	$244.59	3.156%	$252.3093	$252.31	$252.30	$252.30
Purchase #5	$40.39	13.763%	$45.9489	$45.95	$45.95	$45.90
Purchase #6	$211.86	8.623%	$230.1287	$230.13	$230.15	$230.10
Purchase #7	$42.31	5.734%	$44.7361	$44.74	$44.75	$44.70
7 purchase totals =	$982.11		$1,061.7108	$1,061.72	$1,061.75	$1,061.70