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	$201.30	10.750%	$222.9398	$222.94	$222.95	$222.90
Purchase #2	$151.72	10.215%	$167.2182	$167.22	$167.20	$167.20
Purchase #3	$54.50	4.783%	$57.1067	$57.11	$57.10	$57.10
Purchase #4	$53.42	11.242%	$59.4255	$59.43	$59.45	$59.40
Purchase #5	$235.33	13.106%	$266.1723	$266.17	$266.15	$266.20
Purchase #6	$153.29	8.598%	$166.4699	$166.47	$166.45	$166.50
Purchase #7	$26.69	9.197%	$29.1447	$29.14	$29.15	$29.10
7 purchase totals =	$876.25		$968.4771	$968.48	$968.45	$968.40