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	$64.90	4.198%	$67.6245	$67.62	$67.60	$67.60
Purchase #2	$213.98	12.762%	$241.2881	$241.29	$241.30	$241.30
Purchase #3	$223.80	6.533%	$238.4209	$238.42	$238.40	$238.40
Purchase #4	$101.64	10.350%	$112.1597	$112.16	$112.15	$112.20
Purchase #5	$10.64	5.406%	$11.2152	$11.22	$11.20	$11.20
Purchase #6	$213.86	9.242%	$233.6249	$233.62	$233.60	$233.60
Purchase #7	$136.46	12.589%	$153.6389	$153.64	$153.65	$153.60
7 purchase totals =	$965.28		$1,057.9722	$1,057.97	$1,057.90	$1,057.90