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	$137.53	11.626%	$153.5192	$153.52	$153.50	$153.50
Purchase #2	$140.61	7.597%	$151.2921	$151.29	$151.30	$151.30
Purchase #3	$119.83	12.530%	$134.8447	$134.84	$134.85	$134.80
Purchase #4	$232.88	13.532%	$264.3933	$264.39	$264.40	$264.40
Purchase #5	$100.92	7.797%	$108.7887	$108.79	$108.80	$108.80
Purchase #6	$215.49	3.201%	$222.3878	$222.39	$222.40	$222.40
Purchase #7	$61.45	4.292%	$64.0874	$64.09	$64.10	$64.10
7 purchase totals =	$1,008.71		$1,099.3132	$1,099.31	$1,099.35	$1,099.30