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	$175.38	10.724%	$194.1878	$194.19	$194.20	$194.20
Purchase #2	$114.83	11.211%	$127.7036	$127.70	$127.70	$127.70
Purchase #3	$33.66	13.127%	$38.0785	$38.08	$38.10	$38.10
Purchase #4	$99.93	12.610%	$112.5312	$112.53	$112.55	$112.50
Purchase #5	$137.35	10.855%	$152.2593	$152.26	$152.25	$152.30
Purchase #6	$29.65	9.611%	$32.4997	$32.50	$32.50	$32.50
Purchase #7	$52.72	9.112%	$57.5238	$57.52	$57.50	$57.50
7 purchase totals =	$643.52		$714.7839	$714.78	$714.80	$714.80