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	$167.72	9.295%	$183.3096	$183.31	$183.30	$183.30
Purchase #2	$191.43	8.874%	$208.4175	$208.42	$208.40	$208.40
Purchase #3	$17.33	11.111%	$19.2555	$19.26	$19.25	$19.30
Purchase #4	$46.86	4.544%	$48.9893	$48.99	$49.00	$49.00
Purchase #5	$244.32	7.730%	$263.2059	$263.21	$263.20	$263.20
Purchase #6	$230.84	10.599%	$255.3067	$255.31	$255.30	$255.30
Purchase #7	$116.90	12.195%	$131.156	$131.16	$131.15	$131.20
7 purchase totals =	$1,015.40		$1,109.6405	$1,109.66	$1,109.60	$1,109.70