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	$80.88	13.258%	$91.6031	$91.60	$91.60	$91.60
Purchase #2	$245.65	9.784%	$269.6844	$269.68	$269.70	$269.70
Purchase #3	$145.69	4.394%	$152.0916	$152.09	$152.10	$152.10
Purchase #4	$116.80	8.620%	$126.8682	$126.87	$126.85	$126.90
Purchase #5	$13.47	6.820%	$14.3887	$14.39	$14.40	$14.40
Purchase #6	$80.39	12.525%	$90.4588	$90.46	$90.45	$90.50
Purchase #7	$190.92	3.106%	$196.85	$196.85	$196.85	$196.90
7 purchase totals =	$873.80		$941.9448	$941.94	$941.95	$942.10