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	$110.80	10.317%	$122.2312	$122.23	$122.25	$122.20
Purchase #2	$68.79	5.763%	$72.7544	$72.75	$72.75	$72.80
Purchase #3	$79.83	12.865%	$90.1001	$90.10	$90.10	$90.10
Purchase #4	$204.63	4.592%	$214.0266	$214.03	$214.05	$214.00
Purchase #5	$220.59	13.717%	$250.8483	$250.85	$250.85	$250.80
Purchase #6	$90.75	4.578%	$94.9045	$94.90	$94.90	$94.90
Purchase #7	$17.83	9.149%	$19.4613	$19.46	$19.45	$19.50
7 purchase totals =	$793.22		$864.3264	$864.32	$864.35	$864.30