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	$116.78	9.255%	$127.588	$127.59	$127.60	$127.60
Purchase #2	$144.62	7.754%	$155.8338	$155.83	$155.85	$155.80
Purchase #3	$148.81	6.296%	$158.1791	$158.18	$158.20	$158.20
Purchase #4	$201.69	6.476%	$214.7514	$214.75	$214.75	$214.80
Purchase #5	$234.77	6.224%	$249.3821	$249.38	$249.40	$249.40
Purchase #6	$90.45	6.228%	$96.0832	$96.08	$96.10	$96.10
Purchase #7	$98.53	9.212%	$107.6066	$107.61	$107.60	$107.60
7 purchase totals =	$1,035.65		$1,109.4242	$1,109.42	$1,109.50	$1,109.50