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	$79.44	4.257%	$82.8218	$82.82	$82.80	$82.80
Purchase #2	$47.91	4.389%	$50.0128	$50.01	$50.00	$50.00
Purchase #3	$178.51	6.436%	$189.9989	$190.00	$190.00	$190.00
Purchase #4	$144.84	4.162%	$150.8682	$150.87	$150.85	$150.90
Purchase #5	$94.92	5.480%	$100.1216	$100.12	$100.10	$100.10
Purchase #6	$122.86	4.341%	$128.1934	$128.19	$128.20	$128.20
Purchase #7	$126.99	13.680%	$144.3622	$144.36	$144.35	$144.40
7 purchase totals =	$795.47		$846.3789	$846.37	$846.30	$846.40