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	$214.78	13.198%	$243.1267	$243.13	$243.15	$243.10
Purchase #2	$106.59	4.819%	$111.7266	$111.73	$111.75	$111.70
Purchase #3	$183.72	13.689%	$208.8694	$208.87	$208.85	$208.90
Purchase #4	$13.52	5.462%	$14.2585	$14.26	$14.25	$14.30
Purchase #5	$93.58	11.745%	$104.571	$104.57	$104.55	$104.60
Purchase #6	$20.33	3.597%	$21.0613	$21.06	$21.05	$21.10
Purchase #7	$223.57	9.487%	$244.7801	$244.78	$244.80	$244.80
7 purchase totals =	$856.09		$948.3936	$948.40	$948.40	$948.50