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	$173.30	11.382%	$193.025	$193.03	$193.05	$193.00
Purchase #2	$221.29	8.524%	$240.1528	$240.15	$240.15	$240.20
Purchase #3	$34.59	8.598%	$37.564	$37.56	$37.55	$37.60
Purchase #4	$157.47	4.188%	$164.0648	$164.06	$164.05	$164.10
Purchase #5	$46.77	13.471%	$53.0704	$53.07	$53.05	$53.10
Purchase #6	$92.81	13.746%	$105.5677	$105.57	$105.55	$105.60
Purchase #7	$11.37	10.509%	$12.5649	$12.56	$12.55	$12.60
7 purchase totals =	$737.60		$806.0096	$806.00	$805.95	$806.20