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	$144.40	9.823%	$158.5844	$158.58	$158.60	$158.60
Purchase #2	$201.43	10.638%	$222.8581	$222.86	$222.85	$222.90
Purchase #3	$98.89	4.856%	$103.6921	$103.69	$103.70	$103.70
Purchase #4	$103.54	6.611%	$110.385	$110.39	$110.40	$110.40
Purchase #5	$139.87	3.186%	$144.3263	$144.33	$144.35	$144.30
Purchase #6	$109.83	11.801%	$122.791	$122.79	$122.80	$122.80
Purchase #7	$74.67	6.466%	$79.4982	$79.50	$79.50	$79.50
7 purchase totals =	$872.63		$942.1351	$942.14	$942.20	$942.20