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	$245.33	4.178%	$255.5799	$255.58	$255.60	$255.60
Purchase #2	$127.77	13.259%	$144.711	$144.71	$144.70	$144.70
Purchase #3	$50.45	4.687%	$52.8146	$52.81	$52.80	$52.80
Purchase #4	$176.96	11.244%	$196.8574	$196.86	$196.85	$196.90
Purchase #5	$210.60	4.719%	$220.5382	$220.54	$220.55	$220.50
Purchase #6	$114.38	7.684%	$123.169	$123.17	$123.15	$123.20
Purchase #7	$122.87	11.665%	$137.2028	$137.20	$137.20	$137.20
7 purchase totals =	$1,048.36		$1,130.8729	$1,130.87	$1,130.85	$1,130.90