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	$53.25	10.526%	$58.8551	$58.86	$58.85	$58.90
Purchase #2	$103.94	11.262%	$115.6457	$115.65	$115.65	$115.60
Purchase #3	$115.30	10.559%	$127.4745	$127.47	$127.45	$127.50
Purchase #4	$172.66	9.153%	$188.4636	$188.46	$188.45	$188.50
Purchase #5	$143.58	5.856%	$151.988	$151.99	$152.00	$152.00
Purchase #6	$250.33	7.633%	$269.4377	$269.44	$269.45	$269.40
Purchase #7	$138.86	3.410%	$143.5951	$143.60	$143.60	$143.60
7 purchase totals =	$977.92		$1,055.4597	$1,055.47	$1,055.45	$1,055.50