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	$50.42	11.240%	$56.0872	$56.09	$56.10	$56.10
Purchase #2	$138.68	3.585%	$143.6517	$143.65	$143.65	$143.70
Purchase #3	$105.40	5.747%	$111.4573	$111.46	$111.45	$111.50
Purchase #4	$25.79	13.608%	$29.2995	$29.30	$29.30	$29.30
Purchase #5	$57.37	11.626%	$64.0398	$64.04	$64.05	$64.00
Purchase #6	$158.33	5.348%	$166.7975	$166.80	$166.80	$166.80
Purchase #7	$142.45	9.150%	$155.4842	$155.48	$155.50	$155.50
7 purchase totals =	$678.44		$726.8172	$726.82	$726.85	$726.90