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	$217.52	8.285%	$235.5415	$235.54	$235.55	$235.50
Purchase #2	$37.73	9.117%	$41.1698	$41.17	$41.15	$41.20
Purchase #3	$56.88	4.275%	$59.3116	$59.31	$59.30	$59.30
Purchase #4	$170.26	6.450%	$181.2418	$181.24	$181.25	$181.20
Purchase #5	$25.37	9.665%	$27.822	$27.82	$27.80	$27.80
Purchase #6	$96.71	11.497%	$107.8287	$107.83	$107.85	$107.80
Purchase #7	$169.27	12.531%	$190.4812	$190.48	$190.50	$190.50
7 purchase totals =	$773.74		$843.3966	$843.39	$843.40	$843.30