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	$57.48	10.247%	$63.37	$63.37	$63.35	$63.40
Purchase #2	$87.56	3.733%	$90.8286	$90.83	$90.85	$90.80
Purchase #3	$11.72	7.673%	$12.6193	$12.62	$12.60	$12.60
Purchase #4	$134.42	10.427%	$148.436	$148.44	$148.45	$148.40
Purchase #5	$249.34	5.210%	$262.3306	$262.33	$262.35	$262.30
Purchase #6	$33.81	11.279%	$37.6234	$37.62	$37.60	$37.60
Purchase #7	$205.72	13.443%	$233.3749	$233.37	$233.35	$233.40
7 purchase totals =	$780.05		$848.5828	$848.58	$848.55	$848.50