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	$91.71	7.757%	$98.8239	$98.82	$98.80	$98.80
Purchase #2	$86.68	4.714%	$90.7661	$90.77	$90.75	$90.80
Purchase #3	$105.58	5.276%	$111.1504	$111.15	$111.15	$111.20
Purchase #4	$145.66	8.175%	$157.5677	$157.57	$157.55	$157.60
Purchase #5	$67.36	4.444%	$70.3535	$70.35	$70.35	$70.40
Purchase #6	$182.54	9.461%	$199.8101	$199.81	$199.80	$199.80
Purchase #7	$14.30	8.117%	$15.4607	$15.46	$15.45	$15.50
7 purchase totals =	$693.83		$743.9324	$743.93	$743.85	$744.10