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	$180.89	5.863%	$191.4956	$191.50	$191.50	$191.50
Purchase #2	$23.84	6.766%	$25.453	$25.45	$25.45	$25.50
Purchase #3	$108.83	7.795%	$117.3133	$117.31	$117.30	$117.30
Purchase #4	$153.60	12.289%	$172.4759	$172.48	$172.50	$172.50
Purchase #5	$29.39	12.572%	$33.0849	$33.08	$33.10	$33.10
Purchase #6	$94.86	9.320%	$103.701	$103.70	$103.70	$103.70
Purchase #7	$104.62	13.274%	$118.5073	$118.51	$118.50	$118.50
7 purchase totals =	$696.03		$762.0310	$762.03	$762.05	$762.10