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	$60.50	13.670%	$68.7704	$68.77	$68.75	$68.80
Purchase #2	$166.71	5.801%	$176.3808	$176.38	$176.40	$176.40
Purchase #3	$86.75	4.611%	$90.75	$90.75	$90.75	$90.80
Purchase #4	$199.72	12.409%	$224.5033	$224.50	$224.50	$224.50
Purchase #5	$138.78	4.260%	$144.692	$144.69	$144.70	$144.70
Purchase #6	$224.60	3.715%	$232.9439	$232.94	$232.95	$232.90
Purchase #7	$174.40	8.548%	$189.3077	$189.31	$189.30	$189.30
7 purchase totals =	$1,051.46		$1,127.3481	$1,127.34	$1,127.35	$1,127.40