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	$53.76	11.811%	$60.1096	$60.11	$60.10	$60.10
Purchase #2	$134.73	6.456%	$143.4282	$143.43	$143.45	$143.40
Purchase #3	$47.76	7.241%	$51.2183	$51.22	$51.20	$51.20
Purchase #4	$54.68	4.145%	$56.9465	$56.95	$56.95	$56.90
Purchase #5	$243.45	6.317%	$258.8287	$258.83	$258.85	$258.80
Purchase #6	$7.30	5.653%	$7.7127	$7.71	$7.70	$7.70
Purchase #7	$49.85	9.268%	$54.4701	$54.47	$54.45	$54.50
7 purchase totals =	$591.53		$632.7141	$632.72	$632.70	$632.60