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	$154.65	4.379%	$161.4221	$161.42	$161.40	$161.40
Purchase #2	$117.67	4.786%	$123.3017	$123.30	$123.30	$123.30
Purchase #3	$161.25	6.705%	$172.0618	$172.06	$172.05	$172.10
Purchase #4	$130.67	10.799%	$144.7811	$144.78	$144.80	$144.80
Purchase #5	$233.89	12.726%	$263.6548	$263.65	$263.65	$263.70
Purchase #6	$175.47	9.121%	$191.4746	$191.47	$191.45	$191.50
Purchase #7	$113.30	7.166%	$121.4191	$121.42	$121.40	$121.40
7 purchase totals =	$1,086.90		$1,178.1152	$1,178.10	$1,178.05	$1,178.20