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	$16.84	13.167%	$19.0573	$19.06	$19.05	$19.10
Purchase #2	$90.30	11.771%	$100.9292	$100.93	$100.95	$100.90
Purchase #3	$57.76	10.369%	$63.7491	$63.75	$63.75	$63.70
Purchase #4	$116.80	12.865%	$131.8263	$131.83	$131.85	$131.80
Purchase #5	$177.91	3.680%	$184.4571	$184.46	$184.45	$184.50
Purchase #6	$163.99	4.843%	$171.932	$171.93	$171.95	$171.90
Purchase #7	$11.28	11.818%	$12.6131	$12.61	$12.60	$12.60
7 purchase totals =	$634.88		$684.5641	$684.57	$684.60	$684.50