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	$58.97	4.443%	$61.59	$61.59	$61.60	$61.60
Purchase #2	$148.62	9.176%	$162.2574	$162.26	$162.25	$162.30
Purchase #3	$242.33	6.472%	$258.0136	$258.01	$258.00	$258.00
Purchase #4	$161.25	7.291%	$173.0067	$173.01	$173.00	$173.00
Purchase #5	$122.93	4.259%	$128.1656	$128.17	$128.15	$128.20
Purchase #6	$136.36	4.274%	$142.188	$142.19	$142.20	$142.20
Purchase #7	$159.91	11.591%	$178.4452	$178.45	$178.45	$178.40
7 purchase totals =	$1,030.37		$1,103.6665	$1,103.68	$1,103.65	$1,103.70