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	$199.81	5.674%	$211.1472	$211.15	$211.15	$211.10
Purchase #2	$205.52	5.691%	$217.2161	$217.22	$217.20	$217.20
Purchase #3	$225.43	6.670%	$240.4662	$240.47	$240.45	$240.50
Purchase #4	$161.61	7.185%	$173.2217	$173.22	$173.20	$173.20
Purchase #5	$31.82	9.552%	$34.8594	$34.86	$34.85	$34.90
Purchase #6	$52.82	6.141%	$56.0637	$56.06	$56.05	$56.10
Purchase #7	$62.34	8.338%	$67.5379	$67.54	$67.55	$67.50
7 purchase totals =	$939.35		$1,000.5122	$1,000.52	$1,000.45	$1,000.50