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	$244.68	10.271%	$269.8111	$269.81	$269.80	$269.80
Purchase #2	$54.82	12.643%	$61.7509	$61.75	$61.75	$61.80
Purchase #3	$79.97	3.139%	$82.4803	$82.48	$82.50	$82.50
Purchase #4	$127.77	3.544%	$132.2982	$132.30	$132.30	$132.30
Purchase #5	$11.68	8.436%	$12.6653	$12.67	$12.65	$12.70
Purchase #6	$72.95	13.614%	$82.8814	$82.88	$82.90	$82.90
Purchase #7	$77.78	13.247%	$88.0835	$88.08	$88.10	$88.10
7 purchase totals =	$669.65		$729.9707	$729.97	$730.00	$730.10