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	$38.25	13.481%	$43.4065	$43.41	$43.40	$43.40
Purchase #2	$98.47	4.432%	$102.8342	$102.83	$102.85	$102.80
Purchase #3	$140.38	4.291%	$146.4037	$146.40	$146.40	$146.40
Purchase #4	$122.76	3.639%	$127.2272	$127.23	$127.25	$127.20
Purchase #5	$164.95	12.847%	$186.1411	$186.14	$186.15	$186.10
Purchase #6	$119.39	6.699%	$127.3879	$127.39	$127.40	$127.40
Purchase #7	$204.90	11.343%	$228.1418	$228.14	$228.15	$228.10
7 purchase totals =	$889.10		$961.5424	$961.54	$961.60	$961.40