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	$205.27	7.268%	$220.189	$220.19	$220.20	$220.20
Purchase #2	$88.39	9.612%	$96.886	$96.89	$96.90	$96.90
Purchase #3	$187.27	3.106%	$193.0866	$193.09	$193.10	$193.10
Purchase #4	$81.26	5.181%	$85.4701	$85.47	$85.45	$85.50
Purchase #5	$144.88	8.802%	$157.6323	$157.63	$157.65	$157.60
Purchase #6	$103.45	8.720%	$112.4708	$112.47	$112.45	$112.50
Purchase #7	$145.50	5.739%	$153.8502	$153.85	$153.85	$153.90
7 purchase totals =	$956.02		$1,019.5850	$1,019.59	$1,019.60	$1,019.70