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	$108.60	10.384%	$119.877	$119.88	$119.90	$119.90
Purchase #2	$134.53	7.247%	$144.2794	$144.28	$144.30	$144.30
Purchase #3	$51.43	4.422%	$53.7042	$53.70	$53.70	$53.70
Purchase #4	$121.43	3.861%	$126.1184	$126.12	$126.10	$126.10
Purchase #5	$191.55	4.721%	$200.5931	$200.59	$200.60	$200.60
Purchase #6	$180.68	4.448%	$188.7166	$188.72	$188.70	$188.70
Purchase #7	$93.63	6.377%	$99.6008	$99.60	$99.60	$99.60
7 purchase totals =	$881.85		$932.8895	$932.89	$932.90	$932.90