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	$135.27	5.691%	$142.9682	$142.97	$142.95	$143.00
Purchase #2	$233.41	11.120%	$259.3652	$259.37	$259.35	$259.40
Purchase #3	$178.27	10.326%	$196.6782	$196.68	$196.70	$196.70
Purchase #4	$64.38	8.130%	$69.6141	$69.61	$69.60	$69.60
Purchase #5	$224.29	4.269%	$233.8649	$233.86	$233.85	$233.90
Purchase #6	$51.46	6.219%	$54.6603	$54.66	$54.65	$54.70
Purchase #7	$154.82	13.861%	$176.2796	$176.28	$176.30	$176.30
7 purchase totals =	$1,041.90		$1,133.4305	$1,133.43	$1,133.40	$1,133.60