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	$238.42	13.603%	$270.8523	$270.85	$270.85	$270.90
Purchase #2	$172.77	3.105%	$178.1345	$178.13	$178.15	$178.10
Purchase #3	$11.37	3.178%	$11.7313	$11.73	$11.75	$11.70
Purchase #4	$209.84	13.504%	$238.1768	$238.18	$238.20	$238.20
Purchase #5	$126.28	9.613%	$138.4193	$138.42	$138.40	$138.40
Purchase #6	$70.86	3.838%	$73.5796	$73.58	$73.60	$73.60
Purchase #7	$117.98	11.469%	$131.5111	$131.51	$131.50	$131.50
7 purchase totals =	$947.52		$1,042.4049	$1,042.40	$1,042.45	$1,042.40