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	$228.54	9.663%	$250.6238	$250.62	$250.60	$250.60
Purchase #2	$128.98	10.517%	$142.5448	$142.54	$142.55	$142.50
Purchase #3	$164.51	8.523%	$178.5312	$178.53	$178.55	$178.50
Purchase #4	$108.85	5.159%	$114.4656	$114.47	$114.45	$114.50
Purchase #5	$54.78	10.813%	$60.7034	$60.70	$60.70	$60.70
Purchase #6	$224.58	7.542%	$241.5178	$241.52	$241.50	$241.50
Purchase #7	$200.95	5.561%	$212.1248	$212.12	$212.10	$212.10
7 purchase totals =	$1,111.19		$1,200.5114	$1,200.50	$1,200.45	$1,200.40