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	$239.67	9.169%	$261.6453	$261.65	$261.65	$261.60
Purchase #2	$30.31	13.685%	$34.4579	$34.46	$34.45	$34.50
Purchase #3	$118.93	3.456%	$123.0402	$123.04	$123.05	$123.00
Purchase #4	$164.97	13.685%	$187.5461	$187.55	$187.55	$187.50
Purchase #5	$107.86	6.453%	$114.8202	$114.82	$114.80	$114.80
Purchase #6	$213.91	3.365%	$221.1081	$221.11	$221.10	$221.10
Purchase #7	$219.88	4.150%	$229.005	$229.01	$229.00	$229.00
7 purchase totals =	$1,095.53		$1,171.6228	$1,171.64	$1,171.60	$1,171.50