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	$12.73	13.686%	$14.4722	$14.47	$14.45	$14.50
Purchase #2	$75.94	9.214%	$82.9371	$82.94	$82.95	$82.90
Purchase #3	$29.60	7.427%	$31.7984	$31.80	$31.80	$31.80
Purchase #4	$153.29	13.457%	$173.9182	$173.92	$173.90	$173.90
Purchase #5	$149.96	13.218%	$169.7817	$169.78	$169.80	$169.80
Purchase #6	$159.67	4.255%	$166.464	$166.46	$166.45	$166.50
Purchase #7	$181.37	13.366%	$205.6119	$205.61	$205.60	$205.60
7 purchase totals =	$762.56		$844.9835	$844.98	$844.95	$845.00