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	$93.25	7.560%	$100.2997	$100.30	$100.30	$100.30
Purchase #2	$116.47	6.105%	$123.5805	$123.58	$123.60	$123.60
Purchase #3	$112.44	13.238%	$127.3248	$127.32	$127.30	$127.30
Purchase #4	$208.85	8.365%	$226.3203	$226.32	$226.30	$226.30
Purchase #5	$132.38	6.565%	$141.0707	$141.07	$141.05	$141.10
Purchase #6	$194.67	11.418%	$216.8974	$216.90	$216.90	$216.90
Purchase #7	$156.88	13.444%	$177.9709	$177.97	$177.95	$178.00
7 purchase totals =	$1,014.94		$1,113.4643	$1,113.46	$1,113.40	$1,113.50