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	$235.65	11.430%	$262.5848	$262.58	$262.60	$262.60
Purchase #2	$107.47	3.340%	$111.0595	$111.06	$111.05	$111.10
Purchase #3	$36.91	5.247%	$38.8467	$38.85	$38.85	$38.80
Purchase #4	$200.25	8.729%	$217.7298	$217.73	$217.75	$217.70
Purchase #5	$159.78	7.205%	$171.2921	$171.29	$171.30	$171.30
Purchase #6	$110.80	5.874%	$117.3084	$117.31	$117.30	$117.30
Purchase #7	$248.59	5.482%	$262.2177	$262.22	$262.20	$262.20
7 purchase totals =	$1,099.45		$1,181.0390	$1,181.04	$1,181.05	$1,181.00