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	$102.45	13.587%	$116.3699	$116.37	$116.35	$116.40
Purchase #2	$126.76	5.611%	$133.8725	$133.87	$133.85	$133.90
Purchase #3	$204.73	10.211%	$225.635	$225.64	$225.65	$225.60
Purchase #4	$39.69	7.346%	$42.6056	$42.61	$42.60	$42.60
Purchase #5	$140.76	7.514%	$151.3367	$151.34	$151.35	$151.30
Purchase #6	$42.72	6.831%	$45.6382	$45.64	$45.65	$45.60
Purchase #7	$192.88	13.596%	$219.104	$219.10	$219.10	$219.10
7 purchase totals =	$849.99		$934.5619	$934.57	$934.55	$934.50