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	$97.77	13.809%	$111.2711	$111.27	$111.25	$111.30
Purchase #2	$142.75	4.116%	$148.6256	$148.63	$148.65	$148.60
Purchase #3	$48.30	13.793%	$54.962	$54.96	$54.95	$55.00
Purchase #4	$42.60	9.479%	$46.6381	$46.64	$46.65	$46.60
Purchase #5	$227.50	3.495%	$235.4511	$235.45	$235.45	$235.50
Purchase #6	$70.38	11.610%	$78.5511	$78.55	$78.55	$78.60
Purchase #7	$174.52	5.723%	$184.5078	$184.51	$184.50	$184.50
7 purchase totals =	$803.82		$860.0068	$860.01	$860.00	$860.10