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	$97.58	5.792%	$103.2318	$103.23	$103.25	$103.20
Purchase #2	$56.91	10.476%	$62.8719	$62.87	$62.85	$62.90
Purchase #3	$148.37	3.833%	$154.057	$154.06	$154.05	$154.10
Purchase #4	$228.82	13.451%	$259.5986	$259.60	$259.60	$259.60
Purchase #5	$136.34	11.163%	$151.5596	$151.56	$151.55	$151.60
Purchase #6	$51.54	5.796%	$54.5273	$54.53	$54.55	$54.50
Purchase #7	$153.61	8.472%	$166.6238	$166.62	$166.60	$166.60
7 purchase totals =	$873.17		$952.4700	$952.47	$952.45	$952.50