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	$60.83	6.448%	$64.7523	$64.75	$64.75	$64.80
Purchase #2	$216.86	9.209%	$236.8306	$236.83	$236.85	$236.80
Purchase #3	$236.42	8.253%	$255.9317	$255.93	$255.95	$255.90
Purchase #4	$100.87	10.416%	$111.3766	$111.38	$111.40	$111.40
Purchase #5	$107.65	8.467%	$116.7647	$116.76	$116.75	$116.80
Purchase #6	$182.84	5.486%	$192.8706	$192.87	$192.85	$192.90
Purchase #7	$86.30	11.388%	$96.1278	$96.13	$96.15	$96.10
7 purchase totals =	$991.77		$1,074.6543	$1,074.65	$1,074.70	$1,074.70