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	$216.71	6.384%	$230.5448	$230.54	$230.55	$230.50
Purchase #2	$131.67	6.203%	$139.8375	$139.84	$139.85	$139.80
Purchase #3	$205.30	3.150%	$211.767	$211.77	$211.75	$211.80
Purchase #4	$95.31	5.569%	$100.6178	$100.62	$100.60	$100.60
Purchase #5	$160.42	13.648%	$182.3141	$182.31	$182.30	$182.30
Purchase #6	$127.99	12.758%	$144.319	$144.32	$144.30	$144.30
Purchase #7	$30.63	9.523%	$33.5469	$33.55	$33.55	$33.50
7 purchase totals =	$968.03		$1,042.9471	$1,042.95	$1,042.90	$1,042.80