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	$116.77	8.837%	$127.089	$127.09	$127.10	$127.10
Purchase #2	$71.85	9.524%	$78.693	$78.69	$78.70	$78.70
Purchase #3	$171.29	6.589%	$182.5763	$182.58	$182.60	$182.60
Purchase #4	$215.50	12.193%	$241.7759	$241.78	$241.80	$241.80
Purchase #5	$39.87	7.823%	$42.989	$42.99	$43.00	$43.00
Purchase #6	$250.82	6.306%	$266.6367	$266.64	$266.65	$266.60
Purchase #7	$48.85	3.201%	$50.4137	$50.41	$50.40	$50.40
7 purchase totals =	$914.95		$990.1736	$990.18	$990.25	$990.20