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	$247.80	11.255%	$275.6899	$275.69	$275.70	$275.70
Purchase #2	$203.59	12.705%	$229.4561	$229.46	$229.45	$229.50
Purchase #3	$66.71	5.329%	$70.265	$70.27	$70.25	$70.30
Purchase #4	$176.86	5.753%	$187.0348	$187.03	$187.05	$187.00
Purchase #5	$147.89	3.168%	$152.5752	$152.58	$152.60	$152.60
Purchase #6	$60.67	9.432%	$66.3924	$66.39	$66.40	$66.40
Purchase #7	$130.31	4.724%	$136.4658	$136.47	$136.45	$136.50
7 purchase totals =	$1,033.83		$1,117.8792	$1,117.89	$1,117.90	$1,118.00