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	$182.98	9.748%	$200.8169	$200.82	$200.80	$200.80
Purchase #2	$179.85	5.699%	$190.0997	$190.10	$190.10	$190.10
Purchase #3	$92.29	10.380%	$101.8697	$101.87	$101.85	$101.90
Purchase #4	$72.87	5.749%	$77.0593	$77.06	$77.05	$77.10
Purchase #5	$163.78	6.309%	$174.1129	$174.11	$174.10	$174.10
Purchase #6	$69.82	12.861%	$78.7996	$78.80	$78.80	$78.80
Purchase #7	$131.91	4.428%	$137.751	$137.75	$137.75	$137.80
7 purchase totals =	$893.50		$960.5091	$960.51	$960.45	$960.60