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	$107.77	10.652%	$119.2497	$119.25	$119.25	$119.20
Purchase #2	$12.80	8.655%	$13.9078	$13.91	$13.90	$13.90
Purchase #3	$48.38	8.146%	$52.321	$52.32	$52.30	$52.30
Purchase #4	$51.52	4.553%	$53.8657	$53.87	$53.85	$53.90
Purchase #5	$174.51	11.534%	$194.638	$194.64	$194.65	$194.60
Purchase #6	$52.53	8.784%	$57.1442	$57.14	$57.15	$57.10
Purchase #7	$75.50	4.406%	$78.8265	$78.83	$78.85	$78.80
7 purchase totals =	$523.01		$569.9529	$569.96	$569.95	$569.80