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	$148.36	5.760%	$156.9055	$156.91	$156.90	$156.90
Purchase #2	$54.69	8.464%	$59.319	$59.32	$59.30	$59.30
Purchase #3	$139.25	12.798%	$157.0712	$157.07	$157.05	$157.10
Purchase #4	$54.60	3.329%	$56.4176	$56.42	$56.40	$56.40
Purchase #5	$102.98	5.501%	$108.6449	$108.64	$108.65	$108.60
Purchase #6	$101.62	9.475%	$111.2485	$111.25	$111.25	$111.20
Purchase #7	$177.30	4.339%	$184.993	$184.99	$185.00	$185.00
7 purchase totals =	$778.80		$834.5997	$834.60	$834.55	$834.50