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	$107.51	3.317%	$111.0761	$111.08	$111.10	$111.10
Purchase #2	$68.71	10.623%	$76.0091	$76.01	$76.00	$76.00
Purchase #3	$104.44	9.814%	$114.6897	$114.69	$114.70	$114.70
Purchase #4	$118.65	4.639%	$124.1542	$124.15	$124.15	$124.20
Purchase #5	$194.71	9.147%	$212.5201	$212.52	$212.50	$212.50
Purchase #6	$178.40	12.245%	$200.2451	$200.25	$200.25	$200.20
Purchase #7	$90.35	10.410%	$99.7554	$99.76	$99.75	$99.80
7 purchase totals =	$862.77		$938.4497	$938.46	$938.45	$938.50