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	$190.76	5.147%	$200.5784	$200.58	$200.60	$200.60
Purchase #2	$153.28	4.769%	$160.5899	$160.59	$160.60	$160.60
Purchase #3	$134.38	10.278%	$148.1916	$148.19	$148.20	$148.20
Purchase #4	$16.70	8.211%	$18.0712	$18.07	$18.05	$18.10
Purchase #5	$160.69	7.754%	$173.1499	$173.15	$173.15	$173.10
Purchase #6	$226.70	13.421%	$257.1254	$257.13	$257.15	$257.10
Purchase #7	$45.31	11.660%	$50.5931	$50.59	$50.60	$50.60
7 purchase totals =	$927.82		$1,008.2995	$1,008.30	$1,008.35	$1,008.30