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	$142.34	8.430%	$154.3393	$154.34	$154.35	$154.30
Purchase #2	$38.51	13.785%	$43.8186	$43.82	$43.80	$43.80
Purchase #3	$200.52	7.540%	$215.6392	$215.64	$215.65	$215.60
Purchase #4	$38.67	9.258%	$42.2501	$42.25	$42.25	$42.30
Purchase #5	$43.76	10.384%	$48.304	$48.30	$48.30	$48.30
Purchase #6	$47.57	3.233%	$49.1079	$49.11	$49.10	$49.10
Purchase #7	$146.59	13.335%	$166.1378	$166.14	$166.15	$166.10
7 purchase totals =	$657.96		$719.5969	$719.60	$719.60	$719.50