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	$106.72	12.379%	$119.9309	$119.93	$119.95	$119.90
Purchase #2	$29.84	9.613%	$32.7085	$32.71	$32.70	$32.70
Purchase #3	$96.92	3.576%	$100.3859	$100.39	$100.40	$100.40
Purchase #4	$173.50	6.760%	$185.2286	$185.23	$185.25	$185.20
Purchase #5	$176.60	6.548%	$188.1638	$188.16	$188.15	$188.20
Purchase #6	$111.35	11.509%	$124.1653	$124.17	$124.15	$124.20
Purchase #7	$194.79	4.130%	$202.8348	$202.83	$202.85	$202.80
7 purchase totals =	$889.72		$953.4178	$953.42	$953.45	$953.40