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	$180.52	13.765%	$205.3686	$205.37	$205.35	$205.40
Purchase #2	$139.62	10.361%	$154.086	$154.09	$154.10	$154.10
Purchase #3	$183.76	4.214%	$191.5036	$191.50	$191.50	$191.50
Purchase #4	$100.65	3.355%	$104.0268	$104.03	$104.05	$104.00
Purchase #5	$107.29	4.120%	$111.7103	$111.71	$111.70	$111.70
Purchase #6	$123.56	6.493%	$131.5828	$131.58	$131.60	$131.60
Purchase #7	$199.93	3.584%	$207.0955	$207.10	$207.10	$207.10
7 purchase totals =	$1,035.33		$1,105.3736	$1,105.38	$1,105.40	$1,105.40