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	$47.92	9.152%	$52.3056	$52.31	$52.30	$52.30
Purchase #2	$123.31	10.273%	$135.9776	$135.98	$136.00	$136.00
Purchase #3	$101.33	11.295%	$112.7752	$112.78	$112.80	$112.80
Purchase #4	$49.63	9.633%	$54.4109	$54.41	$54.40	$54.40
Purchase #5	$54.27	5.617%	$57.3183	$57.32	$57.30	$57.30
Purchase #6	$172.70	10.486%	$190.8093	$190.81	$190.80	$190.80
Purchase #7	$147.32	7.558%	$158.4544	$158.45	$158.45	$158.50
7 purchase totals =	$696.48		$762.0513	$762.06	$762.05	$762.10