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	$34.75	8.193%	$37.5971	$37.60	$37.60	$37.60
Purchase #2	$214.29	10.105%	$235.944	$235.94	$235.95	$235.90
Purchase #3	$163.50	13.464%	$185.5136	$185.51	$185.50	$185.50
Purchase #4	$56.67	10.544%	$62.6453	$62.65	$62.65	$62.60
Purchase #5	$169.73	3.197%	$175.1563	$175.16	$175.15	$175.20
Purchase #6	$196.25	7.662%	$211.2867	$211.29	$211.30	$211.30
Purchase #7	$54.88	13.465%	$62.2696	$62.27	$62.25	$62.30
7 purchase totals =	$890.07		$970.4126	$970.42	$970.40	$970.40