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	$42.60	7.770%	$45.91	$45.91	$45.90	$45.90
Purchase #2	$225.69	4.578%	$236.0221	$236.02	$236.00	$236.00
Purchase #3	$103.85	3.244%	$107.2189	$107.22	$107.20	$107.20
Purchase #4	$54.56	4.641%	$57.0921	$57.09	$57.10	$57.10
Purchase #5	$148.42	6.483%	$158.0421	$158.04	$158.05	$158.00
Purchase #6	$107.85	3.203%	$111.3044	$111.30	$111.30	$111.30
Purchase #7	$10.56	8.493%	$11.4569	$11.46	$11.45	$11.50
7 purchase totals =	$693.53		$727.0465	$727.04	$727.00	$727.00