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	$75.93	7.665%	$81.75	$81.75	$81.75	$81.80
Purchase #2	$115.87	10.193%	$127.6806	$127.68	$127.70	$127.70
Purchase #3	$105.94	3.135%	$109.2612	$109.26	$109.25	$109.30
Purchase #4	$184.84	13.651%	$210.0725	$210.07	$210.05	$210.10
Purchase #5	$242.35	13.606%	$275.3241	$275.32	$275.30	$275.30
Purchase #6	$124.64	7.852%	$134.4267	$134.43	$134.45	$134.40
Purchase #7	$84.33	6.628%	$89.9194	$89.92	$89.90	$89.90
7 purchase totals =	$933.90		$1,028.4345	$1,028.43	$1,028.40	$1,028.50