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	$49.85	9.178%	$54.4252	$54.43	$54.45	$54.40
Purchase #2	$188.52	10.735%	$208.7576	$208.76	$208.75	$208.80
Purchase #3	$212.25	5.663%	$224.2697	$224.27	$224.25	$224.30
Purchase #4	$53.76	10.554%	$59.4338	$59.43	$59.45	$59.40
Purchase #5	$152.82	13.410%	$173.3132	$173.31	$173.30	$173.30
Purchase #6	$184.60	12.758%	$208.1513	$208.15	$208.15	$208.20
Purchase #7	$211.95	3.255%	$218.849	$218.85	$218.85	$218.80
7 purchase totals =	$1,053.75		$1,147.1998	$1,147.20	$1,147.20	$1,147.20