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	$119.65	3.529%	$123.8724	$123.87	$123.85	$123.90
Purchase #2	$126.72	9.301%	$138.5062	$138.51	$138.50	$138.50
Purchase #3	$122.97	11.551%	$137.1743	$137.17	$137.15	$137.20
Purchase #4	$220.86	8.199%	$238.9683	$238.97	$238.95	$239.00
Purchase #5	$83.83	10.267%	$92.4368	$92.44	$92.45	$92.40
Purchase #6	$140.98	3.211%	$145.5069	$145.51	$145.50	$145.50
Purchase #7	$205.71	7.834%	$221.8253	$221.83	$221.85	$221.80
7 purchase totals =	$1,020.72		$1,098.2902	$1,098.30	$1,098.25	$1,098.30