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	$220.32	4.440%	$230.1022	$230.10	$230.10	$230.10
Purchase #2	$137.93	13.338%	$156.3271	$156.33	$156.35	$156.30
Purchase #3	$176.52	12.254%	$198.1508	$198.15	$198.15	$198.20
Purchase #4	$249.45	3.574%	$258.3653	$258.37	$258.35	$258.40
Purchase #5	$40.86	9.139%	$44.5942	$44.59	$44.60	$44.60
Purchase #6	$137.89	12.497%	$155.1221	$155.12	$155.10	$155.10
Purchase #7	$43.81	11.329%	$48.7732	$48.77	$48.75	$48.80
7 purchase totals =	$1,006.78		$1,091.4349	$1,091.43	$1,091.40	$1,091.50