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	$115.89	9.469%	$126.8636	$126.86	$126.85	$126.90
Purchase #2	$54.89	5.177%	$57.7317	$57.73	$57.75	$57.70
Purchase #3	$79.40	3.762%	$82.387	$82.39	$82.40	$82.40
Purchase #4	$118.54	7.148%	$127.0132	$127.01	$127.00	$127.00
Purchase #5	$172.42	4.716%	$180.5513	$180.55	$180.55	$180.60
Purchase #6	$146.49	13.855%	$166.7862	$166.79	$166.80	$166.80
Purchase #7	$220.45	7.710%	$237.4467	$237.45	$237.45	$237.40
7 purchase totals =	$908.08		$978.7797	$978.78	$978.80	$978.80