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	$183.36	5.132%	$192.77	$192.77	$192.75	$192.80
Purchase #2	$74.61	5.149%	$78.4517	$78.45	$78.45	$78.50
Purchase #3	$99.82	4.671%	$104.4826	$104.48	$104.50	$104.50
Purchase #4	$17.78	8.557%	$19.3014	$19.30	$19.30	$19.30
Purchase #5	$43.97	10.468%	$48.5728	$48.57	$48.55	$48.60
Purchase #6	$10.37	4.404%	$10.8267	$10.83	$10.85	$10.80
Purchase #7	$56.83	9.204%	$62.0606	$62.06	$62.05	$62.10
7 purchase totals =	$486.74		$516.4658	$516.46	$516.45	$516.60