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	$209.35	5.398%	$220.6507	$220.65	$220.65	$220.70
Purchase #2	$107.81	8.391%	$116.8563	$116.86	$116.85	$116.90
Purchase #3	$130.43	6.808%	$139.3097	$139.31	$139.30	$139.30
Purchase #4	$142.54	9.810%	$156.5232	$156.52	$156.50	$156.50
Purchase #5	$105.69	4.624%	$110.5771	$110.58	$110.60	$110.60
Purchase #6	$153.35	3.446%	$158.6344	$158.63	$158.65	$158.60
Purchase #7	$168.61	7.718%	$181.6233	$181.62	$181.60	$181.60
7 purchase totals =	$1,017.78		$1,084.1747	$1,084.17	$1,084.15	$1,084.20