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	$181.38	5.592%	$191.5228	$191.52	$191.50	$191.50
Purchase #2	$115.37	3.648%	$119.5787	$119.58	$119.60	$119.60
Purchase #3	$194.86	5.357%	$205.2987	$205.30	$205.30	$205.30
Purchase #4	$230.87	10.607%	$255.3584	$255.36	$255.35	$255.40
Purchase #5	$132.64	3.406%	$137.1577	$137.16	$137.15	$137.20
Purchase #6	$213.31	8.471%	$231.3795	$231.38	$231.40	$231.40
Purchase #7	$145.43	8.364%	$157.5938	$157.59	$157.60	$157.60
7 purchase totals =	$1,213.86		$1,297.8896	$1,297.89	$1,297.90	$1,298.00