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	$225.94	10.357%	$249.3406	$249.34	$249.35	$249.30
Purchase #2	$201.59	3.318%	$208.2788	$208.28	$208.30	$208.30
Purchase #3	$205.91	13.589%	$233.8911	$233.89	$233.90	$233.90
Purchase #4	$194.34	7.772%	$209.4441	$209.44	$209.45	$209.40
Purchase #5	$48.60	10.806%	$53.8517	$53.85	$53.85	$53.90
Purchase #6	$126.73	13.104%	$143.3367	$143.34	$143.35	$143.30
Purchase #7	$44.32	9.452%	$48.5091	$48.51	$48.50	$48.50
7 purchase totals =	$1,047.43		$1,146.6521	$1,146.65	$1,146.70	$1,146.60