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	$248.58	7.528%	$267.2931	$267.29	$267.30	$267.30
Purchase #2	$209.50	7.105%	$224.385	$224.39	$224.40	$224.40
Purchase #3	$29.62	8.716%	$32.2017	$32.20	$32.20	$32.20
Purchase #4	$62.25	5.369%	$65.5922	$65.59	$65.60	$65.60
Purchase #5	$234.31	8.862%	$255.0746	$255.07	$255.05	$255.10
Purchase #6	$85.25	12.436%	$95.8517	$95.85	$95.85	$95.90
Purchase #7	$98.46	12.810%	$111.0727	$111.07	$111.05	$111.10
7 purchase totals =	$967.97		$1,051.4710	$1,051.46	$1,051.45	$1,051.60