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	$59.73	9.843%	$65.6092	$65.61	$65.60	$65.60
Purchase #2	$79.62	4.612%	$83.2921	$83.29	$83.30	$83.30
Purchase #3	$194.83	10.271%	$214.841	$214.84	$214.85	$214.80
Purchase #4	$49.83	13.593%	$56.6034	$56.60	$56.60	$56.60
Purchase #5	$169.92	7.783%	$183.1449	$183.14	$183.15	$183.10
Purchase #6	$124.72	5.267%	$131.289	$131.29	$131.30	$131.30
Purchase #7	$63.96	9.592%	$70.095	$70.10	$70.10	$70.10
7 purchase totals =	$742.61		$804.8746	$804.87	$804.90	$804.80