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	$69.85	12.717%	$78.7328	$78.73	$78.75	$78.70
Purchase #2	$152.30	4.217%	$158.7225	$158.72	$158.70	$158.70
Purchase #3	$183.30	11.817%	$204.9606	$204.96	$204.95	$205.00
Purchase #4	$227.73	3.162%	$234.9308	$234.93	$234.95	$234.90
Purchase #5	$201.96	10.118%	$222.3943	$222.39	$222.40	$222.40
Purchase #6	$45.78	12.341%	$51.4297	$51.43	$51.45	$51.40
Purchase #7	$100.95	5.641%	$106.6446	$106.64	$106.65	$106.60
7 purchase totals =	$981.87		$1,057.8153	$1,057.80	$1,057.85	$1,057.70