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	$43.55	10.533%	$48.1371	$48.14	$48.15	$48.10
Purchase #2	$224.72	12.384%	$252.5493	$252.55	$252.55	$252.50
Purchase #3	$5.51	4.642%	$5.7658	$5.77	$5.75	$5.80
Purchase #4	$191.82	4.680%	$200.7972	$200.80	$200.80	$200.80
Purchase #5	$122.43	5.310%	$128.931	$128.93	$128.95	$128.90
Purchase #6	$101.52	7.832%	$109.471	$109.47	$109.45	$109.50
Purchase #7	$69.28	4.777%	$72.5895	$72.59	$72.60	$72.60
7 purchase totals =	$758.83		$818.2409	$818.25	$818.25	$818.20