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	$69.31	13.663%	$78.7798	$78.78	$78.80	$78.80
Purchase #2	$104.79	5.744%	$110.8091	$110.81	$110.80	$110.80
Purchase #3	$41.95	7.501%	$45.0967	$45.10	$45.10	$45.10
Purchase #4	$7.36	7.832%	$7.9364	$7.94	$7.95	$7.90
Purchase #5	$192.83	3.685%	$199.9358	$199.94	$199.95	$199.90
Purchase #6	$5.87	8.784%	$6.3856	$6.39	$6.40	$6.40
Purchase #7	$111.27	7.471%	$119.583	$119.58	$119.60	$119.60
7 purchase totals =	$533.38		$568.5264	$568.54	$568.60	$568.50