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	$106.27	5.208%	$111.8045	$111.80	$111.80	$111.80
Purchase #2	$184.90	13.361%	$209.6045	$209.60	$209.60	$209.60
Purchase #3	$36.26	3.136%	$37.3971	$37.40	$37.40	$37.40
Purchase #4	$132.65	6.776%	$141.6384	$141.64	$141.65	$141.60
Purchase #5	$103.77	7.135%	$111.174	$111.17	$111.15	$111.20
Purchase #6	$50.68	3.442%	$52.4244	$52.42	$52.40	$52.40
Purchase #7	$29.89	3.422%	$30.9128	$30.91	$30.90	$30.90
7 purchase totals =	$644.42		$694.9557	$694.94	$694.90	$694.90