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	$132.81	5.724%	$140.412	$140.41	$140.40	$140.40
Purchase #2	$79.80	13.461%	$90.5419	$90.54	$90.55	$90.50
Purchase #3	$104.92	7.125%	$112.3956	$112.40	$112.40	$112.40
Purchase #4	$216.28	5.244%	$227.6217	$227.62	$227.60	$227.60
Purchase #5	$43.32	10.860%	$48.0246	$48.02	$48.00	$48.00
Purchase #6	$113.87	8.835%	$123.9304	$123.93	$123.95	$123.90
Purchase #7	$222.45	9.592%	$243.7874	$243.79	$243.80	$243.80
7 purchase totals =	$913.45		$986.7136	$986.71	$986.70	$986.60