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	$95.54	5.473%	$100.7689	$100.77	$100.75	$100.80
Purchase #2	$144.64	4.106%	$150.5789	$150.58	$150.60	$150.60
Purchase #3	$207.80	5.786%	$219.8233	$219.82	$219.80	$219.80
Purchase #4	$29.46	10.347%	$32.5082	$32.51	$32.50	$32.50
Purchase #5	$69.42	11.851%	$77.647	$77.65	$77.65	$77.60
Purchase #6	$132.47	10.592%	$146.5012	$146.50	$146.50	$146.50
Purchase #7	$241.80	12.613%	$272.2982	$272.30	$272.30	$272.30
7 purchase totals =	$921.13		$1,000.1257	$1,000.13	$1,000.10	$1,000.10