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	$78.25	5.448%	$82.5131	$82.51	$82.50	$82.50
Purchase #2	$29.46	13.727%	$33.504	$33.50	$33.50	$33.50
Purchase #3	$158.55	9.340%	$173.3586	$173.36	$173.35	$173.40
Purchase #4	$236.32	10.275%	$260.6019	$260.60	$260.60	$260.60
Purchase #5	$188.29	5.499%	$198.6441	$198.64	$198.65	$198.60
Purchase #6	$13.43	11.863%	$15.0232	$15.02	$15.00	$15.00
Purchase #7	$66.39	10.821%	$73.5741	$73.57	$73.55	$73.60
7 purchase totals =	$770.69		$837.2190	$837.20	$837.15	$837.20