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	$174.34	3.754%	$180.8847	$180.88	$180.90	$180.90
Purchase #2	$50.89	7.344%	$54.6274	$54.63	$54.65	$54.60
Purchase #3	$10.72	8.599%	$11.6418	$11.64	$11.65	$11.60
Purchase #4	$85.44	12.182%	$95.8483	$95.85	$95.85	$95.80
Purchase #5	$6.52	12.133%	$7.3111	$7.31	$7.30	$7.30
Purchase #6	$126.97	5.240%	$133.6232	$133.62	$133.60	$133.60
Purchase #7	$142.88	5.730%	$151.067	$151.07	$151.05	$151.10
7 purchase totals =	$597.76		$635.0035	$635.00	$635.00	$634.90