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	$101.25	10.470%	$111.8509	$111.85	$111.85	$111.90
Purchase #2	$109.62	13.509%	$124.4286	$124.43	$124.45	$124.40
Purchase #3	$125.59	10.788%	$139.1386	$139.14	$139.15	$139.10
Purchase #4	$119.67	11.637%	$133.596	$133.60	$133.60	$133.60
Purchase #5	$138.34	3.779%	$143.5679	$143.57	$143.55	$143.60
Purchase #6	$136.43	5.693%	$144.197	$144.20	$144.20	$144.20
Purchase #7	$205.38	6.613%	$218.9618	$218.96	$218.95	$219.00
7 purchase totals =	$936.28		$1,015.7408	$1,015.75	$1,015.75	$1,015.80