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	$179.45	4.810%	$188.0815	$188.08	$188.10	$188.10
Purchase #2	$70.96	10.630%	$78.503	$78.50	$78.50	$78.50
Purchase #3	$134.45	12.395%	$151.1151	$151.12	$151.10	$151.10
Purchase #4	$180.76	6.188%	$191.9454	$191.95	$191.95	$191.90
Purchase #5	$43.86	13.730%	$49.882	$49.88	$49.90	$49.90
Purchase #6	$38.84	9.637%	$42.583	$42.58	$42.60	$42.60
Purchase #7	$99.83	3.607%	$103.4309	$103.43	$103.45	$103.40
7 purchase totals =	$748.15		$805.5409	$805.54	$805.60	$805.50