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	$160.33	7.277%	$171.9972	$172.00	$172.00	$172.00
Purchase #2	$167.38	12.469%	$188.2506	$188.25	$188.25	$188.30
Purchase #3	$49.44	9.835%	$54.3024	$54.30	$54.30	$54.30
Purchase #4	$163.71	10.802%	$181.394	$181.39	$181.40	$181.40
Purchase #5	$235.26	8.860%	$256.104	$256.10	$256.10	$256.10
Purchase #6	$246.78	6.522%	$262.875	$262.88	$262.90	$262.90
Purchase #7	$92.86	10.339%	$102.4608	$102.46	$102.45	$102.50
7 purchase totals =	$1,115.76		$1,217.3840	$1,217.38	$1,217.40	$1,217.50