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	$10.48	6.130%	$11.1224	$11.12	$11.10	$11.10
Purchase #2	$193.37	12.399%	$217.3459	$217.35	$217.35	$217.30
Purchase #3	$151.68	8.388%	$164.4029	$164.40	$164.40	$164.40
Purchase #4	$107.86	3.737%	$111.8907	$111.89	$111.90	$111.90
Purchase #5	$134.94	6.412%	$143.5924	$143.59	$143.60	$143.60
Purchase #6	$136.75	6.828%	$146.0873	$146.09	$146.10	$146.10
Purchase #7	$195.97	6.176%	$208.0731	$208.07	$208.05	$208.10
7 purchase totals =	$931.05		$1,002.5147	$1,002.51	$1,002.50	$1,002.50