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	$249.89	7.163%	$267.7896	$267.79	$267.80	$267.80
Purchase #2	$247.27	4.118%	$257.4526	$257.45	$257.45	$257.50
Purchase #3	$227.61	12.217%	$255.4171	$255.42	$255.40	$255.40
Purchase #4	$196.89	5.587%	$207.8902	$207.89	$207.90	$207.90
Purchase #5	$9.49	6.860%	$10.141	$10.14	$10.15	$10.10
Purchase #6	$113.77	3.853%	$118.1536	$118.15	$118.15	$118.20
Purchase #7	$127.92	9.123%	$139.5901	$139.59	$139.60	$139.60
7 purchase totals =	$1,172.84		$1,256.4342	$1,256.43	$1,256.45	$1,256.50