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	$43.65	10.299%	$48.1455	$48.15	$48.15	$48.10
Purchase #2	$145.96	11.209%	$162.3207	$162.32	$162.30	$162.30
Purchase #3	$173.44	7.719%	$186.8278	$186.83	$186.85	$186.80
Purchase #4	$134.27	12.198%	$150.6483	$150.65	$150.65	$150.60
Purchase #5	$143.63	10.275%	$158.388	$158.39	$158.40	$158.40
Purchase #6	$135.59	11.680%	$151.4269	$151.43	$151.45	$151.40
Purchase #7	$197.75	10.196%	$217.9126	$217.91	$217.90	$217.90
7 purchase totals =	$974.29		$1,075.6698	$1,075.68	$1,075.70	$1,075.50