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	$108.95	13.111%	$123.2344	$123.23	$123.25	$123.20
Purchase #2	$26.81	12.195%	$30.0795	$30.08	$30.10	$30.10
Purchase #3	$96.69	8.848%	$105.2451	$105.25	$105.25	$105.20
Purchase #4	$162.86	3.496%	$168.5536	$168.55	$168.55	$168.60
Purchase #5	$160.59	7.823%	$173.153	$173.15	$173.15	$173.20
Purchase #6	$213.31	9.258%	$233.0582	$233.06	$233.05	$233.10
Purchase #7	$235.82	10.553%	$260.7061	$260.71	$260.70	$260.70
7 purchase totals =	$1,005.03		$1,094.0299	$1,094.03	$1,094.05	$1,094.10