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	$158.62	9.364%	$173.4732	$173.47	$173.45	$173.50
Purchase #2	$109.62	5.247%	$115.3718	$115.37	$115.35	$115.40
Purchase #3	$41.46	5.478%	$43.7312	$43.73	$43.75	$43.70
Purchase #4	$111.96	5.540%	$118.1626	$118.16	$118.15	$118.20
Purchase #5	$185.31	5.700%	$195.8727	$195.87	$195.85	$195.90
Purchase #6	$113.77	8.235%	$123.139	$123.14	$123.15	$123.10
Purchase #7	$120.78	9.275%	$131.9823	$131.98	$132.00	$132.00
7 purchase totals =	$841.52		$901.7328	$901.72	$901.70	$901.80