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	$56.90	10.200%	$62.7038	$62.70	$62.70	$62.70
Purchase #2	$89.65	3.624%	$92.8989	$92.90	$92.90	$92.90
Purchase #3	$165.52	4.856%	$173.5577	$173.56	$173.55	$173.60
Purchase #4	$121.37	5.178%	$127.6545	$127.65	$127.65	$127.70
Purchase #5	$148.39	12.241%	$166.5544	$166.55	$166.55	$166.60
Purchase #6	$76.95	4.118%	$80.1188	$80.12	$80.10	$80.10
Purchase #7	$139.93	12.217%	$157.0252	$157.03	$157.05	$157.00
7 purchase totals =	$798.71		$860.5133	$860.51	$860.50	$860.60