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	$241.48	5.667%	$255.1647	$255.16	$255.15	$255.20
Purchase #2	$116.31	9.358%	$127.1943	$127.19	$127.20	$127.20
Purchase #3	$111.29	8.625%	$120.8888	$120.89	$120.90	$120.90
Purchase #4	$161.70	3.169%	$166.8243	$166.82	$166.80	$166.80
Purchase #5	$135.72	11.660%	$151.545	$151.55	$151.55	$151.50
Purchase #6	$176.58	7.446%	$189.7281	$189.73	$189.75	$189.70
Purchase #7	$42.86	6.525%	$45.6566	$45.66	$45.65	$45.70
7 purchase totals =	$985.94		$1,057.0018	$1,057.00	$1,057.00	$1,057.00