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	$46.41	4.714%	$48.5978	$48.60	$48.60	$48.60
Purchase #2	$203.78	6.453%	$216.9299	$216.93	$216.95	$216.90
Purchase #3	$238.65	10.593%	$263.9302	$263.93	$263.95	$263.90
Purchase #4	$211.43	10.777%	$234.2158	$234.22	$234.20	$234.20
Purchase #5	$12.78	5.768%	$13.5172	$13.52	$13.50	$13.50
Purchase #6	$187.96	4.738%	$196.8655	$196.87	$196.85	$196.90
Purchase #7	$96.70	9.561%	$105.9455	$105.95	$105.95	$105.90
7 purchase totals =	$997.71		$1,080.0019	$1,080.02	$1,080.00	$1,079.90