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	$141.98	9.238%	$155.0961	$155.10	$155.10	$155.10
Purchase #2	$122.88	13.550%	$139.5302	$139.53	$139.55	$139.50
Purchase #3	$67.73	4.431%	$70.7311	$70.73	$70.75	$70.70
Purchase #4	$36.88	3.817%	$38.2877	$38.29	$38.30	$38.30
Purchase #5	$101.65	10.328%	$112.1484	$112.15	$112.15	$112.10
Purchase #6	$146.50	13.599%	$166.4225	$166.42	$166.40	$166.40
Purchase #7	$183.81	3.153%	$189.6055	$189.61	$189.60	$189.60
7 purchase totals =	$801.43		$871.8215	$871.83	$871.85	$871.70