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	$88.27	13.644%	$100.3136	$100.31	$100.30	$100.30
Purchase #2	$45.58	4.439%	$47.6033	$47.60	$47.60	$47.60
Purchase #3	$246.82	6.358%	$262.5128	$262.51	$262.50	$262.50
Purchase #4	$136.40	5.725%	$144.2089	$144.21	$144.20	$144.20
Purchase #5	$234.40	7.834%	$252.7629	$252.76	$252.75	$252.80
Purchase #6	$116.35	7.105%	$124.6167	$124.62	$124.60	$124.60
Purchase #7	$79.55	6.326%	$84.5823	$84.58	$84.60	$84.60
7 purchase totals =	$947.37		$1,016.6005	$1,016.59	$1,016.55	$1,016.60