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	$158.89	4.635%	$166.2546	$166.25	$166.25	$166.30
Purchase #2	$50.28	12.242%	$56.4353	$56.44	$56.45	$56.40
Purchase #3	$174.54	4.387%	$182.1971	$182.20	$182.20	$182.20
Purchase #4	$101.82	8.447%	$110.4207	$110.42	$110.40	$110.40
Purchase #5	$198.50	13.628%	$225.5516	$225.55	$225.55	$225.60
Purchase #6	$157.42	6.463%	$167.5941	$167.59	$167.60	$167.60
Purchase #7	$228.26	13.657%	$259.4335	$259.43	$259.45	$259.40
7 purchase totals =	$1,069.71		$1,167.8869	$1,167.88	$1,167.90	$1,167.90