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	$241.80	10.393%	$266.9303	$266.93	$266.95	$266.90
Purchase #2	$28.50	12.493%	$32.0605	$32.06	$32.05	$32.10
Purchase #3	$34.41	4.426%	$35.933	$35.93	$35.95	$35.90
Purchase #4	$141.46	12.310%	$158.8737	$158.87	$158.85	$158.90
Purchase #5	$197.82	7.591%	$212.8365	$212.84	$212.85	$212.80
Purchase #6	$120.65	5.329%	$127.0794	$127.08	$127.10	$127.10
Purchase #7	$36.83	12.116%	$41.2923	$41.29	$41.30	$41.30
7 purchase totals =	$801.47		$875.0057	$875.00	$875.05	$875.00