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	$106.68	9.760%	$117.092	$117.09	$117.10	$117.10
Purchase #2	$37.55	12.538%	$42.258	$42.26	$42.25	$42.30
Purchase #3	$167.46	9.552%	$183.4558	$183.46	$183.45	$183.50
Purchase #4	$24.76	13.750%	$28.1645	$28.16	$28.15	$28.20
Purchase #5	$111.93	13.690%	$127.2532	$127.25	$127.25	$127.30
Purchase #6	$104.46	6.748%	$111.509	$111.51	$111.50	$111.50
Purchase #7	$244.39	9.622%	$267.9052	$267.91	$267.90	$267.90
7 purchase totals =	$797.23		$877.6377	$877.64	$877.60	$877.80