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	$244.47	6.712%	$260.8788	$260.88	$260.90	$260.90
Purchase #2	$83.86	7.486%	$90.1378	$90.14	$90.15	$90.10
Purchase #3	$190.82	9.413%	$208.7819	$208.78	$208.80	$208.80
Purchase #4	$189.81	5.136%	$199.5586	$199.56	$199.55	$199.60
Purchase #5	$47.70	10.787%	$52.8454	$52.85	$52.85	$52.80
Purchase #6	$65.37	4.444%	$68.275	$68.28	$68.30	$68.30
Purchase #7	$197.34	3.640%	$204.5232	$204.52	$204.50	$204.50
7 purchase totals =	$1,019.37		$1,085.0007	$1,085.01	$1,085.05	$1,085.00