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	$175.78	7.281%	$188.5785	$188.58	$188.60	$188.60
Purchase #2	$145.50	7.492%	$156.4009	$156.40	$156.40	$156.40
Purchase #3	$62.29	6.189%	$66.1451	$66.15	$66.15	$66.10
Purchase #4	$127.45	3.130%	$131.4392	$131.44	$131.45	$131.40
Purchase #5	$196.31	10.521%	$216.9638	$216.96	$216.95	$217.00
Purchase #6	$212.83	13.247%	$241.0236	$241.02	$241.00	$241.00
Purchase #7	$100.50	13.403%	$113.97	$113.97	$113.95	$114.00
7 purchase totals =	$1,020.66		$1,114.5211	$1,114.52	$1,114.50	$1,114.50