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	$108.65	13.434%	$123.246	$123.25	$123.25	$123.20
Purchase #2	$172.68	12.576%	$194.3962	$194.40	$194.40	$194.40
Purchase #3	$132.44	5.786%	$140.103	$140.10	$140.10	$140.10
Purchase #4	$178.99	3.376%	$185.0327	$185.03	$185.05	$185.00
Purchase #5	$49.82	9.140%	$54.3735	$54.37	$54.35	$54.40
Purchase #6	$151.63	9.772%	$166.4473	$166.45	$166.45	$166.40
Purchase #7	$145.72	4.598%	$152.4202	$152.42	$152.40	$152.40
7 purchase totals =	$939.93		$1,016.0189	$1,016.02	$1,016.00	$1,015.90