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	$142.82	6.780%	$152.5032	$152.50	$152.50	$152.50
Purchase #2	$77.49	7.824%	$83.5528	$83.55	$83.55	$83.60
Purchase #3	$198.66	11.247%	$221.0033	$221.00	$221.00	$221.00
Purchase #4	$230.43	4.707%	$241.2763	$241.28	$241.30	$241.30
Purchase #5	$202.72	10.462%	$223.9286	$223.93	$223.95	$223.90
Purchase #6	$84.82	11.511%	$94.5836	$94.58	$94.60	$94.60
Purchase #7	$49.34	11.513%	$55.0205	$55.02	$55.00	$55.00
7 purchase totals =	$986.28		$1,071.8683	$1,071.86	$1,071.90	$1,071.90