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	$217.89	5.837%	$230.6082	$230.61	$230.60	$230.60
Purchase #2	$235.38	5.141%	$247.4809	$247.48	$247.50	$247.50
Purchase #3	$211.84	4.701%	$221.7986	$221.80	$221.80	$221.80
Purchase #4	$158.72	4.858%	$166.4306	$166.43	$166.45	$166.40
Purchase #5	$166.27	12.612%	$187.24	$187.24	$187.25	$187.20
Purchase #6	$105.84	5.699%	$111.8718	$111.87	$111.85	$111.90
Purchase #7	$148.33	4.416%	$154.8803	$154.88	$154.90	$154.90
7 purchase totals =	$1,244.27		$1,320.3104	$1,320.31	$1,320.35	$1,320.30