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	$133.70	7.736%	$144.043	$144.04	$144.05	$144.00
Purchase #2	$153.94	12.471%	$173.1379	$173.14	$173.15	$173.10
Purchase #3	$158.85	8.366%	$172.1394	$172.14	$172.15	$172.10
Purchase #4	$90.59	8.487%	$98.2784	$98.28	$98.30	$98.30
Purchase #5	$228.59	10.413%	$252.3931	$252.39	$252.40	$252.40
Purchase #6	$176.44	11.465%	$196.6688	$196.67	$196.65	$196.70
Purchase #7	$119.92	6.340%	$127.5229	$127.52	$127.50	$127.50
7 purchase totals =	$1,062.03		$1,164.1835	$1,164.18	$1,164.20	$1,164.10