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	$13.99	4.198%	$14.5773	$14.58	$14.60	$14.60
Purchase #2	$36.60	7.840%	$39.4694	$39.47	$39.45	$39.50
Purchase #3	$121.27	10.221%	$133.665	$133.67	$133.65	$133.70
Purchase #4	$98.75	12.538%	$111.1313	$111.13	$111.15	$111.10
Purchase #5	$47.37	3.144%	$48.8593	$48.86	$48.85	$48.90
Purchase #6	$248.37	6.539%	$264.6109	$264.61	$264.60	$264.60
Purchase #7	$99.57	6.216%	$105.7593	$105.76	$105.75	$105.80
7 purchase totals =	$665.92		$718.0725	$718.08	$718.05	$718.20