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	$9.72	10.341%	$10.7251	$10.73	$10.75	$10.70
Purchase #2	$137.51	6.597%	$146.5815	$146.58	$146.60	$146.60
Purchase #3	$177.25	13.164%	$200.5832	$200.58	$200.60	$200.60
Purchase #4	$60.74	7.787%	$65.4698	$65.47	$65.45	$65.50
Purchase #5	$183.33	12.162%	$205.6266	$205.63	$205.65	$205.60
Purchase #6	$233.44	12.591%	$262.8324	$262.83	$262.85	$262.80
Purchase #7	$67.87	6.251%	$72.1126	$72.11	$72.10	$72.10
7 purchase totals =	$869.86		$963.9312	$963.93	$964.00	$963.90