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	$67.27	6.855%	$71.8814	$71.88	$71.90	$71.90
Purchase #2	$238.60	11.307%	$265.5785	$265.58	$265.60	$265.60
Purchase #3	$15.36	3.763%	$15.938	$15.94	$15.95	$15.90
Purchase #4	$127.67	3.790%	$132.5087	$132.51	$132.50	$132.50
Purchase #5	$182.66	4.874%	$191.5628	$191.56	$191.55	$191.60
Purchase #6	$156.26	10.225%	$172.2376	$172.24	$172.25	$172.20
Purchase #7	$166.82	8.806%	$181.5102	$181.51	$181.50	$181.50
7 purchase totals =	$954.64		$1,031.2172	$1,031.22	$1,031.25	$1,031.20