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	$222.95	6.496%	$237.4328	$237.43	$237.45	$237.40
Purchase #2	$214.70	7.736%	$231.3092	$231.31	$231.30	$231.30
Purchase #3	$18.98	3.202%	$19.5877	$19.59	$19.60	$19.60
Purchase #4	$77.55	5.444%	$81.7718	$81.77	$81.75	$81.80
Purchase #5	$62.52	4.792%	$65.516	$65.52	$65.50	$65.50
Purchase #6	$53.86	10.313%	$59.4146	$59.41	$59.40	$59.40
Purchase #7	$174.71	3.863%	$181.459	$181.46	$181.45	$181.50
7 purchase totals =	$825.27		$876.4911	$876.49	$876.45	$876.50