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	$61.30	8.136%	$66.2874	$66.29	$66.30	$66.30
Purchase #2	$17.84	13.779%	$20.2982	$20.30	$20.30	$20.30
Purchase #3	$236.77	4.372%	$247.1216	$247.12	$247.10	$247.10
Purchase #4	$72.27	8.646%	$78.5185	$78.52	$78.50	$78.50
Purchase #5	$173.39	10.874%	$192.2444	$192.24	$192.25	$192.20
Purchase #6	$101.88	3.658%	$105.6068	$105.61	$105.60	$105.60
Purchase #7	$244.48	11.573%	$272.7737	$272.77	$272.75	$272.80
7 purchase totals =	$907.93		$982.8506	$982.85	$982.80	$982.80