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	$127.80	7.583%	$137.4911	$137.49	$137.50	$137.50
Purchase #2	$172.98	11.450%	$192.7862	$192.79	$192.80	$192.80
Purchase #3	$32.56	13.773%	$37.0445	$37.04	$37.05	$37.00
Purchase #4	$171.66	3.856%	$178.2792	$178.28	$178.30	$178.30
Purchase #5	$244.48	4.404%	$255.2469	$255.25	$255.25	$255.20
Purchase #6	$159.38	8.161%	$172.387	$172.39	$172.40	$172.40
Purchase #7	$160.51	13.298%	$181.8546	$181.85	$181.85	$181.90
7 purchase totals =	$1,069.37		$1,155.0895	$1,155.09	$1,155.15	$1,155.10