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	$179.86	11.741%	$200.9774	$200.98	$201.00	$201.00
Purchase #2	$212.39	12.338%	$238.5947	$238.59	$238.60	$238.60
Purchase #3	$155.87	4.571%	$162.9948	$162.99	$163.00	$163.00
Purchase #4	$176.94	7.580%	$190.3521	$190.35	$190.35	$190.40
Purchase #5	$172.82	10.285%	$190.5945	$190.59	$190.60	$190.60
Purchase #6	$21.50	12.640%	$24.2176	$24.22	$24.20	$24.20
Purchase #7	$14.34	5.385%	$15.1122	$15.11	$15.10	$15.10
7 purchase totals =	$933.72		$1,022.8433	$1,022.83	$1,022.85	$1,022.90