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	$189.39	5.653%	$200.0962	$200.10	$200.10	$200.10
Purchase #2	$122.60	11.850%	$137.1281	$137.13	$137.15	$137.10
Purchase #3	$167.35	10.480%	$184.8883	$184.89	$184.90	$184.90
Purchase #4	$59.71	4.652%	$62.4877	$62.49	$62.50	$62.50
Purchase #5	$66.93	5.395%	$70.5409	$70.54	$70.55	$70.50
Purchase #6	$218.92	13.699%	$248.9099	$248.91	$248.90	$248.90
Purchase #7	$166.91	3.863%	$173.3577	$173.36	$173.35	$173.40
7 purchase totals =	$991.81		$1,077.4088	$1,077.42	$1,077.45	$1,077.40