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	$107.43	3.782%	$111.493	$111.49	$111.50	$111.50
Purchase #2	$95.42	10.321%	$105.2683	$105.27	$105.25	$105.30
Purchase #3	$115.94	6.504%	$123.4807	$123.48	$123.50	$123.50
Purchase #4	$101.33	6.173%	$107.5851	$107.59	$107.60	$107.60
Purchase #5	$18.96	3.851%	$19.6901	$19.69	$19.70	$19.70
Purchase #6	$94.70	9.489%	$103.6861	$103.69	$103.70	$103.70
Purchase #7	$187.80	8.731%	$204.1968	$204.20	$204.20	$204.20
7 purchase totals =	$721.58		$775.4001	$775.41	$775.45	$775.50