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	$70.96	8.589%	$77.0548	$77.05	$77.05	$77.10
Purchase #2	$151.84	13.701%	$172.6436	$172.64	$172.65	$172.60
Purchase #3	$60.51	4.589%	$63.2868	$63.29	$63.30	$63.30
Purchase #4	$198.71	9.239%	$217.0688	$217.07	$217.05	$217.10
Purchase #5	$107.73	3.541%	$111.5447	$111.54	$111.55	$111.50
Purchase #6	$24.85	9.321%	$27.1663	$27.17	$27.15	$27.20
Purchase #7	$151.91	3.147%	$156.6906	$156.69	$156.70	$156.70
7 purchase totals =	$766.51		$825.4556	$825.45	$825.45	$825.50