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	$235.26	6.649%	$250.9024	$250.90	$250.90	$250.90
Purchase #2	$248.92	3.691%	$258.1076	$258.11	$258.10	$258.10
Purchase #3	$100.45	4.435%	$104.905	$104.91	$104.90	$104.90
Purchase #4	$115.98	9.742%	$127.2788	$127.28	$127.30	$127.30
Purchase #5	$5.53	8.732%	$6.0129	$6.01	$6.00	$6.00
Purchase #6	$55.94	10.855%	$62.0123	$62.01	$62.00	$62.00
Purchase #7	$139.27	10.189%	$153.4602	$153.46	$153.45	$153.50
7 purchase totals =	$901.35		$962.6792	$962.68	$962.65	$962.70