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	$151.43	11.270%	$168.4962	$168.50	$168.50	$168.50
Purchase #2	$29.68	13.715%	$33.7506	$33.75	$33.75	$33.80
Purchase #3	$49.28	10.832%	$54.618	$54.62	$54.60	$54.60
Purchase #4	$38.95	3.562%	$40.3374	$40.34	$40.35	$40.30
Purchase #5	$109.62	5.405%	$115.545	$115.55	$115.55	$115.50
Purchase #6	$219.90	4.822%	$230.5036	$230.50	$230.50	$230.50
Purchase #7	$42.59	6.271%	$45.2608	$45.26	$45.25	$45.30
7 purchase totals =	$641.45		$688.5116	$688.52	$688.50	$688.50