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	$244.94	7.665%	$263.7147	$263.71	$263.70	$263.70
Purchase #2	$79.74	12.573%	$89.7657	$89.77	$89.75	$89.80
Purchase #3	$112.60	13.141%	$127.3968	$127.40	$127.40	$127.40
Purchase #4	$59.43	12.448%	$66.8278	$66.83	$66.85	$66.80
Purchase #5	$60.42	4.236%	$62.9794	$62.98	$63.00	$63.00
Purchase #6	$83.71	13.159%	$94.7254	$94.73	$94.75	$94.70
Purchase #7	$130.55	6.136%	$138.5605	$138.56	$138.55	$138.60
7 purchase totals =	$771.39		$843.9703	$843.98	$844.00	$844.00