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	$55.79	8.634%	$60.6069	$60.61	$60.60	$60.60
Purchase #2	$9.32	7.397%	$10.0094	$10.01	$10.00	$10.00
Purchase #3	$79.72	8.424%	$86.4356	$86.44	$86.45	$86.40
Purchase #4	$81.55	10.485%	$90.1005	$90.10	$90.10	$90.10
Purchase #5	$99.90	12.353%	$112.2406	$112.24	$112.25	$112.20
Purchase #6	$212.50	4.182%	$221.3868	$221.39	$221.40	$221.40
Purchase #7	$196.40	6.248%	$208.6711	$208.67	$208.65	$208.70
7 purchase totals =	$735.18		$789.4509	$789.46	$789.45	$789.40