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	$10.95	5.480%	$11.5501	$11.55	$11.55	$11.60
Purchase #2	$97.25	6.203%	$103.2824	$103.28	$103.30	$103.30
Purchase #3	$240.89	9.143%	$262.9146	$262.91	$262.90	$262.90
Purchase #4	$101.54	4.177%	$105.7813	$105.78	$105.80	$105.80
Purchase #5	$89.27	13.641%	$101.4473	$101.45	$101.45	$101.40
Purchase #6	$220.99	10.649%	$244.5232	$244.52	$244.50	$244.50
Purchase #7	$145.30	13.616%	$165.084	$165.08	$165.10	$165.10
7 purchase totals =	$906.19		$994.5829	$994.57	$994.60	$994.60