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	$139.38	6.688%	$148.7017	$148.70	$148.70	$148.70
Purchase #2	$103.28	6.453%	$109.9447	$109.94	$109.95	$109.90
Purchase #3	$59.43	12.214%	$66.6888	$66.69	$66.70	$66.70
Purchase #4	$239.92	6.116%	$254.5935	$254.59	$254.60	$254.60
Purchase #5	$122.77	13.667%	$139.549	$139.55	$139.55	$139.50
Purchase #6	$184.62	4.293%	$192.5457	$192.55	$192.55	$192.50
Purchase #7	$142.55	5.279%	$150.0752	$150.08	$150.10	$150.10
7 purchase totals =	$991.95		$1,062.0986	$1,062.10	$1,062.15	$1,062.00