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	$104.68	11.247%	$116.4534	$116.45	$116.45	$116.50
Purchase #2	$240.60	9.368%	$263.1394	$263.14	$263.15	$263.10
Purchase #3	$39.69	8.849%	$43.2022	$43.20	$43.20	$43.20
Purchase #4	$103.44	7.477%	$111.1742	$111.17	$111.15	$111.20
Purchase #5	$27.37	3.599%	$28.355	$28.36	$28.35	$28.40
Purchase #6	$69.35	13.369%	$78.6214	$78.62	$78.60	$78.60
Purchase #7	$79.58	4.506%	$83.1659	$83.17	$83.15	$83.20
7 purchase totals =	$664.71		$724.1115	$724.11	$724.05	$724.20