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	$207.69	8.152%	$224.6209	$224.62	$224.60	$224.60
Purchase #2	$190.40	7.682%	$205.0265	$205.03	$205.05	$205.00
Purchase #3	$122.40	7.748%	$131.8836	$131.88	$131.90	$131.90
Purchase #4	$168.31	5.172%	$177.015	$177.02	$177.00	$177.00
Purchase #5	$34.90	12.822%	$39.3749	$39.37	$39.35	$39.40
Purchase #6	$172.42	7.541%	$185.4222	$185.42	$185.40	$185.40
Purchase #7	$95.66	4.335%	$99.8069	$99.81	$99.80	$99.80
7 purchase totals =	$991.78		$1,063.1500	$1,063.15	$1,063.10	$1,063.10