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	$136.62	5.324%	$143.8936	$143.89	$143.90	$143.90
Purchase #2	$58.56	5.240%	$61.6285	$61.63	$61.65	$61.60
Purchase #3	$159.32	8.272%	$172.499	$172.50	$172.50	$172.50
Purchase #4	$162.90	6.653%	$173.7377	$173.74	$173.75	$173.70
Purchase #5	$63.85	4.433%	$66.6805	$66.68	$66.70	$66.70
Purchase #6	$13.25	5.111%	$13.9272	$13.93	$13.95	$13.90
Purchase #7	$209.65	9.161%	$228.856	$228.86	$228.85	$228.90
7 purchase totals =	$804.15		$861.2225	$861.23	$861.30	$861.20