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	$67.52	4.600%	$70.6259	$70.63	$70.65	$70.60
Purchase #2	$184.37	4.535%	$192.7312	$192.73	$192.75	$192.70
Purchase #3	$68.93	12.794%	$77.7489	$77.75	$77.75	$77.70
Purchase #4	$171.30	4.379%	$178.8012	$178.80	$178.80	$178.80
Purchase #5	$184.67	6.522%	$196.7142	$196.71	$196.70	$196.70
Purchase #6	$146.31	6.352%	$155.6036	$155.60	$155.60	$155.60
Purchase #7	$176.40	10.199%	$194.391	$194.39	$194.40	$194.40
7 purchase totals =	$999.50		$1,066.6160	$1,066.61	$1,066.65	$1,066.50