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	$171.43	8.594%	$186.1627	$186.16	$186.15	$186.20
Purchase #2	$235.77	3.774%	$244.668	$244.67	$244.65	$244.70
Purchase #3	$145.84	3.543%	$151.0071	$151.01	$151.00	$151.00
Purchase #4	$173.40	5.569%	$183.0566	$183.06	$183.05	$183.10
Purchase #5	$39.82	4.141%	$41.4689	$41.47	$41.45	$41.50
Purchase #6	$61.95	7.185%	$66.4011	$66.40	$66.40	$66.40
Purchase #7	$126.85	13.547%	$144.0344	$144.03	$144.05	$144.00
7 purchase totals =	$955.06		$1,016.7988	$1,016.80	$1,016.75	$1,016.90