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	$51.39	6.703%	$54.8347	$54.83	$54.85	$54.80
Purchase #2	$98.66	12.769%	$111.2579	$111.26	$111.25	$111.30
Purchase #3	$229.77	4.856%	$240.9276	$240.93	$240.95	$240.90
Purchase #4	$190.43	7.816%	$205.314	$205.31	$205.30	$205.30
Purchase #5	$146.25	6.138%	$155.2268	$155.23	$155.25	$155.20
Purchase #6	$117.86	7.800%	$127.0531	$127.05	$127.05	$127.10
Purchase #7	$221.52	3.104%	$228.396	$228.40	$228.40	$228.40
7 purchase totals =	$1,055.88		$1,123.0101	$1,123.01	$1,123.05	$1,123.00