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	$90.76	5.167%	$95.4496	$95.45	$95.45	$95.40
Purchase #2	$199.92	11.771%	$223.4526	$223.45	$223.45	$223.50
Purchase #3	$84.55	6.727%	$90.2377	$90.24	$90.25	$90.20
Purchase #4	$82.98	5.562%	$87.5953	$87.60	$87.60	$87.60
Purchase #5	$54.75	10.163%	$60.3142	$60.31	$60.30	$60.30
Purchase #6	$10.29	3.476%	$10.6477	$10.65	$10.65	$10.60
Purchase #7	$208.96	10.204%	$230.2823	$230.28	$230.30	$230.30
7 purchase totals =	$732.21		$797.9794	$797.98	$798.00	$797.90