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	$107.42	3.331%	$110.9982	$111.00	$111.00	$111.00
Purchase #2	$51.52	5.611%	$54.4108	$54.41	$54.40	$54.40
Purchase #3	$86.48	4.332%	$90.2263	$90.23	$90.25	$90.20
Purchase #4	$83.43	13.189%	$94.4336	$94.43	$94.45	$94.40
Purchase #5	$158.56	6.622%	$169.0598	$169.06	$169.05	$169.10
Purchase #6	$100.54	7.313%	$107.8925	$107.89	$107.90	$107.90
Purchase #7	$224.73	3.741%	$233.1371	$233.14	$233.15	$233.10
7 purchase totals =	$812.68		$860.1583	$860.16	$860.20	$860.10