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	$62.70	11.133%	$69.6804	$69.68	$69.70	$69.70
Purchase #2	$102.49	13.264%	$116.0843	$116.08	$116.10	$116.10
Purchase #3	$235.91	12.587%	$265.604	$265.60	$265.60	$265.60
Purchase #4	$173.82	8.844%	$189.1926	$189.19	$189.20	$189.20
Purchase #5	$71.54	4.702%	$74.9038	$74.90	$74.90	$74.90
Purchase #6	$166.96	10.866%	$185.1019	$185.10	$185.10	$185.10
Purchase #7	$100.52	11.328%	$111.9069	$111.91	$111.90	$111.90
7 purchase totals =	$913.94		$1,012.4739	$1,012.46	$1,012.50	$1,012.50