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	$230.30	13.493%	$261.3744	$261.37	$261.35	$261.40
Purchase #2	$50.77	5.232%	$53.4263	$53.43	$53.45	$53.40
Purchase #3	$191.74	10.868%	$212.5783	$212.58	$212.60	$212.60
Purchase #4	$173.95	4.503%	$181.783	$181.78	$181.80	$181.80
Purchase #5	$54.67	12.524%	$61.5169	$61.52	$61.50	$61.50
Purchase #6	$25.99	5.688%	$27.4683	$27.47	$27.45	$27.50
Purchase #7	$89.95	7.686%	$96.8636	$96.86	$96.85	$96.90
7 purchase totals =	$817.37		$895.0108	$895.01	$895.00	$895.10