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	$227.45	6.187%	$241.5223	$241.52	$241.50	$241.50
Purchase #2	$84.31	7.115%	$90.3087	$90.31	$90.30	$90.30
Purchase #3	$105.47	6.647%	$112.4806	$112.48	$112.50	$112.50
Purchase #4	$141.40	10.390%	$156.0915	$156.09	$156.10	$156.10
Purchase #5	$47.42	6.666%	$50.581	$50.58	$50.60	$50.60
Purchase #6	$172.92	6.304%	$183.8209	$183.82	$183.80	$183.80
Purchase #7	$177.86	6.115%	$188.7361	$188.74	$188.75	$188.70
7 purchase totals =	$956.83		$1,023.5411	$1,023.54	$1,023.55	$1,023.50