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	$182.31	5.395%	$192.1456	$192.15	$192.15	$192.10
Purchase #2	$247.45	3.601%	$256.3607	$256.36	$256.35	$256.40
Purchase #3	$157.83	6.591%	$168.2326	$168.23	$168.25	$168.20
Purchase #4	$158.59	4.845%	$166.2737	$166.27	$166.25	$166.30
Purchase #5	$115.78	10.590%	$128.0411	$128.04	$128.05	$128.00
Purchase #6	$126.65	6.403%	$134.7594	$134.76	$134.75	$134.80
Purchase #7	$109.26	6.703%	$116.5837	$116.58	$116.60	$116.60
7 purchase totals =	$1,097.87		$1,162.3968	$1,162.39	$1,162.40	$1,162.40