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	$63.92	6.280%	$67.9342	$67.93	$67.95	$67.90
Purchase #2	$37.53	13.532%	$42.6086	$42.61	$42.60	$42.60
Purchase #3	$197.52	12.444%	$222.0994	$222.10	$222.10	$222.10
Purchase #4	$104.43	13.131%	$118.1427	$118.14	$118.15	$118.10
Purchase #5	$124.60	6.699%	$132.947	$132.95	$132.95	$132.90
Purchase #6	$246.85	4.348%	$257.583	$257.58	$257.60	$257.60
Purchase #7	$62.43	6.587%	$66.5423	$66.54	$66.55	$66.50
7 purchase totals =	$837.28		$907.8572	$907.85	$907.90	$907.70