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	$193.66	10.697%	$214.3758	$214.38	$214.40	$214.40
Purchase #2	$178.79	10.141%	$196.9211	$196.92	$196.90	$196.90
Purchase #3	$64.43	13.418%	$73.0752	$73.08	$73.10	$73.10
Purchase #4	$69.32	4.634%	$72.5323	$72.53	$72.55	$72.50
Purchase #5	$76.45	9.119%	$83.4215	$83.42	$83.40	$83.40
Purchase #6	$101.65	4.567%	$106.2924	$106.29	$106.30	$106.30
Purchase #7	$9.84	6.419%	$10.4716	$10.47	$10.45	$10.50
7 purchase totals =	$694.14		$757.0899	$757.09	$757.10	$757.10