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	$67.64	13.788%	$76.9662	$76.97	$76.95	$77.00
Purchase #2	$50.56	12.162%	$56.7091	$56.71	$56.70	$56.70
Purchase #3	$78.90	7.319%	$84.6747	$84.67	$84.65	$84.70
Purchase #4	$158.72	12.289%	$178.2251	$178.23	$178.25	$178.20
Purchase #5	$105.73	5.566%	$111.6149	$111.61	$111.60	$111.60
Purchase #6	$179.31	8.447%	$194.4563	$194.46	$194.45	$194.50
Purchase #7	$89.89	5.834%	$95.1342	$95.13	$95.15	$95.10
7 purchase totals =	$730.75		$797.7805	$797.78	$797.75	$797.80