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	$101.40	3.488%	$104.9368	$104.94	$104.95	$104.90
Purchase #2	$145.43	5.151%	$152.9211	$152.92	$152.90	$152.90
Purchase #3	$153.27	12.808%	$172.9008	$172.90	$172.90	$172.90
Purchase #4	$215.90	5.149%	$227.0167	$227.02	$227.00	$227.00
Purchase #5	$104.35	9.856%	$114.6347	$114.63	$114.65	$114.60
Purchase #6	$83.56	7.809%	$90.0852	$90.09	$90.10	$90.10
Purchase #7	$95.32	7.757%	$102.714	$102.71	$102.70	$102.70
7 purchase totals =	$899.23		$965.2093	$965.21	$965.20	$965.10