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	$178.28	6.719%	$190.2586	$190.26	$190.25	$190.30
Purchase #2	$239.38	4.309%	$249.6949	$249.69	$249.70	$249.70
Purchase #3	$200.87	4.741%	$210.3932	$210.39	$210.40	$210.40
Purchase #4	$107.84	4.730%	$112.9408	$112.94	$112.95	$112.90
Purchase #5	$184.94	13.490%	$209.8884	$209.89	$209.90	$209.90
Purchase #6	$114.97	11.789%	$128.5238	$128.52	$128.50	$128.50
Purchase #7	$144.95	4.552%	$151.5481	$151.55	$151.55	$151.50
7 purchase totals =	$1,171.23		$1,253.2478	$1,253.24	$1,253.25	$1,253.20