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	$203.43	13.673%	$231.245	$231.25	$231.25	$231.20
Purchase #2	$107.77	3.102%	$111.113	$111.11	$111.10	$111.10
Purchase #3	$64.43	13.174%	$72.918	$72.92	$72.90	$72.90
Purchase #4	$93.93	3.169%	$96.9066	$96.91	$96.90	$96.90
Purchase #5	$22.52	8.284%	$24.3856	$24.39	$24.40	$24.40
Purchase #6	$110.38	6.611%	$117.6772	$117.68	$117.70	$117.70
Purchase #7	$39.26	3.758%	$40.7354	$40.74	$40.75	$40.70
7 purchase totals =	$641.72		$694.9808	$695.00	$695.00	$694.90