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	$58.56	10.337%	$64.6133	$64.61	$64.60	$64.60
Purchase #2	$78.66	5.442%	$82.9407	$82.94	$82.95	$82.90
Purchase #3	$184.79	6.262%	$196.3615	$196.36	$196.35	$196.40
Purchase #4	$95.47	7.812%	$102.9281	$102.93	$102.95	$102.90
Purchase #5	$79.99	10.505%	$88.3929	$88.39	$88.40	$88.40
Purchase #6	$12.85	3.431%	$13.2909	$13.29	$13.30	$13.30
Purchase #7	$106.87	4.793%	$111.9923	$111.99	$112.00	$112.00
7 purchase totals =	$617.19		$660.5197	$660.51	$660.55	$660.50