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	$80.55	11.521%	$89.8302	$89.83	$89.85	$89.80
Purchase #2	$12.82	10.376%	$14.1502	$14.15	$14.15	$14.20
Purchase #3	$38.29	13.306%	$43.3849	$43.38	$43.40	$43.40
Purchase #4	$219.87	4.687%	$230.1753	$230.18	$230.20	$230.20
Purchase #5	$45.28	7.266%	$48.57	$48.57	$48.55	$48.60
Purchase #6	$19.43	12.116%	$21.7841	$21.78	$21.80	$21.80
Purchase #7	$123.70	3.799%	$128.3994	$128.40	$128.40	$128.40
7 purchase totals =	$539.94		$576.2941	$576.29	$576.35	$576.40