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	$161.53	3.627%	$167.3887	$167.39	$167.40	$167.40
Purchase #2	$43.52	7.684%	$46.8641	$46.86	$46.85	$46.90
Purchase #3	$131.84	9.572%	$144.4597	$144.46	$144.45	$144.50
Purchase #4	$144.66	13.465%	$164.1385	$164.14	$164.15	$164.10
Purchase #5	$148.57	7.547%	$159.7826	$159.78	$159.80	$159.80
Purchase #6	$157.60	5.395%	$166.1025	$166.10	$166.10	$166.10
Purchase #7	$200.51	4.401%	$209.3344	$209.33	$209.35	$209.30
7 purchase totals =	$988.23		$1,058.0705	$1,058.06	$1,058.10	$1,058.10