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	$11.28	8.767%	$12.2689	$12.27	$12.25	$12.30
Purchase #2	$46.84	3.839%	$48.6382	$48.64	$48.65	$48.60
Purchase #3	$54.87	13.507%	$62.2813	$62.28	$62.30	$62.30
Purchase #4	$212.47	3.481%	$219.8661	$219.87	$219.85	$219.90
Purchase #5	$36.45	4.265%	$38.0046	$38.00	$38.00	$38.00
Purchase #6	$61.51	3.493%	$63.6585	$63.66	$63.65	$63.70
Purchase #7	$79.90	12.516%	$89.9003	$89.90	$89.90	$89.90
7 purchase totals =	$503.32		$534.6179	$534.62	$534.60	$534.70