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	$127.75	9.163%	$139.4557	$139.46	$139.45	$139.50
Purchase #2	$205.38	10.363%	$226.6635	$226.66	$226.65	$226.70
Purchase #3	$248.61	11.394%	$276.9366	$276.94	$276.95	$276.90
Purchase #4	$196.80	13.342%	$223.0571	$223.06	$223.05	$223.10
Purchase #5	$201.58	4.107%	$209.8589	$209.86	$209.85	$209.90
Purchase #6	$122.28	4.142%	$127.3448	$127.34	$127.35	$127.30
Purchase #7	$223.75	13.794%	$254.6141	$254.61	$254.60	$254.60
7 purchase totals =	$1,326.15		$1,457.9307	$1,457.93	$1,457.90	$1,458.00