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	$144.83	6.162%	$153.7544	$153.75	$153.75	$153.80
Purchase #2	$166.70	13.812%	$189.7246	$189.72	$189.70	$189.70
Purchase #3	$176.37	4.165%	$183.7158	$183.72	$183.70	$183.70
Purchase #4	$82.54	8.271%	$89.3669	$89.37	$89.35	$89.40
Purchase #5	$41.43	12.661%	$46.6755	$46.68	$46.70	$46.70
Purchase #6	$119.67	9.584%	$131.1392	$131.14	$131.15	$131.10
Purchase #7	$84.52	7.590%	$90.9351	$90.94	$90.95	$90.90
7 purchase totals =	$816.06		$885.3115	$885.32	$885.30	$885.30