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	$137.32	9.802%	$150.7801	$150.78	$150.80	$150.80
Purchase #2	$214.47	5.630%	$226.5447	$226.54	$226.55	$226.50
Purchase #3	$84.40	9.818%	$92.6864	$92.69	$92.70	$92.70
Purchase #4	$187.93	3.558%	$194.6165	$194.62	$194.60	$194.60
Purchase #5	$116.91	13.453%	$132.6379	$132.64	$132.65	$132.60
Purchase #6	$200.37	11.567%	$223.5468	$223.55	$223.55	$223.50
Purchase #7	$62.92	5.130%	$66.1478	$66.15	$66.15	$66.10
7 purchase totals =	$1,004.32		$1,086.9602	$1,086.97	$1,087.00	$1,086.80