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	$105.55	10.330%	$116.4533	$116.45	$116.45	$116.50
Purchase #2	$70.93	10.718%	$78.5323	$78.53	$78.55	$78.50
Purchase #3	$228.66	8.676%	$248.4985	$248.50	$248.50	$248.50
Purchase #4	$123.86	12.619%	$139.4899	$139.49	$139.50	$139.50
Purchase #5	$124.70	4.408%	$130.1968	$130.20	$130.20	$130.20
Purchase #6	$200.98	13.213%	$227.5355	$227.54	$227.55	$227.50
Purchase #7	$203.35	13.426%	$230.6518	$230.65	$230.65	$230.70
7 purchase totals =	$1,058.03		$1,171.3581	$1,171.36	$1,171.40	$1,171.40