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	$140.72	9.849%	$154.5795	$154.58	$154.60	$154.60
Purchase #2	$54.95	7.573%	$59.1114	$59.11	$59.10	$59.10
Purchase #3	$5.95	10.869%	$6.5967	$6.60	$6.60	$6.60
Purchase #4	$123.38	10.539%	$136.383	$136.38	$136.40	$136.40
Purchase #5	$127.39	11.370%	$141.8742	$141.87	$141.85	$141.90
Purchase #6	$49.30	6.602%	$52.5548	$52.55	$52.55	$52.60
Purchase #7	$242.94	8.395%	$263.3348	$263.33	$263.35	$263.30
7 purchase totals =	$744.63		$814.4344	$814.42	$814.45	$814.50