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	$223.31	13.377%	$253.1822	$253.18	$253.20	$253.20
Purchase #2	$197.51	8.694%	$214.6815	$214.68	$214.70	$214.70
Purchase #3	$159.44	7.265%	$171.0233	$171.02	$171.00	$171.00
Purchase #4	$163.93	10.750%	$181.5525	$181.55	$181.55	$181.60
Purchase #5	$97.89	13.798%	$111.3969	$111.40	$111.40	$111.40
Purchase #6	$118.91	7.335%	$127.632	$127.63	$127.65	$127.60
Purchase #7	$78.83	12.405%	$88.6089	$88.61	$88.60	$88.60
7 purchase totals =	$1,039.82		$1,148.0773	$1,148.07	$1,148.10	$1,148.10