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	$115.34	3.706%	$119.6145	$119.61	$119.60	$119.60
Purchase #2	$130.46	7.240%	$139.9053	$139.91	$139.90	$139.90
Purchase #3	$128.63	6.675%	$137.2161	$137.22	$137.20	$137.20
Purchase #4	$21.99	10.822%	$24.3698	$24.37	$24.35	$24.40
Purchase #5	$21.54	5.477%	$22.7197	$22.72	$22.70	$22.70
Purchase #6	$230.63	11.230%	$256.5297	$256.53	$256.55	$256.50
Purchase #7	$217.31	7.474%	$233.5517	$233.55	$233.55	$233.60
7 purchase totals =	$865.90		$933.9068	$933.91	$933.85	$933.90