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	$172.92	13.408%	$196.1051	$196.11	$196.10	$196.10
Purchase #2	$175.77	10.142%	$193.5966	$193.60	$193.60	$193.60
Purchase #3	$216.83	5.188%	$228.0791	$228.08	$228.10	$228.10
Purchase #4	$68.31	3.207%	$70.5007	$70.50	$70.50	$70.50
Purchase #5	$164.64	8.321%	$178.3397	$178.34	$178.35	$178.30
Purchase #6	$158.38	11.577%	$176.7157	$176.72	$176.70	$176.70
Purchase #7	$167.38	13.589%	$190.1253	$190.13	$190.15	$190.10
7 purchase totals =	$1,124.23		$1,233.4622	$1,233.48	$1,233.50	$1,233.40