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	$199.42	9.726%	$218.8156	$218.82	$218.80	$218.80
Purchase #2	$57.67	6.455%	$61.3926	$61.39	$61.40	$61.40
Purchase #3	$45.75	3.436%	$47.322	$47.32	$47.30	$47.30
Purchase #4	$19.90	9.171%	$21.725	$21.73	$21.75	$21.70
Purchase #5	$161.99	8.177%	$175.2359	$175.24	$175.25	$175.20
Purchase #6	$63.78	3.664%	$66.1169	$66.12	$66.10	$66.10
Purchase #7	$123.33	3.411%	$127.5368	$127.54	$127.55	$127.50
7 purchase totals =	$671.84		$718.1448	$718.16	$718.15	$718.00