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	$100.89	13.608%	$114.6191	$114.62	$114.60	$114.60
Purchase #2	$19.94	8.238%	$21.5827	$21.58	$21.60	$21.60
Purchase #3	$135.43	4.328%	$141.2914	$141.29	$141.30	$141.30
Purchase #4	$45.57	6.239%	$48.4131	$48.41	$48.40	$48.40
Purchase #5	$104.88	10.716%	$116.1189	$116.12	$116.10	$116.10
Purchase #6	$146.35	10.299%	$161.4226	$161.42	$161.40	$161.40
Purchase #7	$208.32	5.557%	$219.8963	$219.90	$219.90	$219.90
7 purchase totals =	$761.38		$823.3441	$823.34	$823.30	$823.30