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	$24.76	3.398%	$25.6013	$25.60	$25.60	$25.60
Purchase #2	$203.91	6.371%	$216.9011	$216.90	$216.90	$216.90
Purchase #3	$63.70	13.743%	$72.4543	$72.45	$72.45	$72.50
Purchase #4	$158.33	9.625%	$173.5693	$173.57	$173.55	$173.60
Purchase #5	$196.73	7.379%	$211.2467	$211.25	$211.25	$211.20
Purchase #6	$100.60	10.620%	$111.2837	$111.28	$111.30	$111.30
Purchase #7	$10.45	12.213%	$11.7263	$11.73	$11.75	$11.70
7 purchase totals =	$758.48		$822.7827	$822.78	$822.80	$822.80