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	$152.28	7.348%	$163.4695	$163.47	$163.45	$163.50
Purchase #2	$42.81	7.102%	$45.8504	$45.85	$45.85	$45.90
Purchase #3	$132.90	6.318%	$141.2966	$141.30	$141.30	$141.30
Purchase #4	$72.59	6.109%	$77.0245	$77.02	$77.00	$77.00
Purchase #5	$44.71	4.619%	$46.7752	$46.78	$46.80	$46.80
Purchase #6	$82.41	9.296%	$90.0708	$90.07	$90.05	$90.10
Purchase #7	$90.45	6.291%	$96.1402	$96.14	$96.15	$96.10
7 purchase totals =	$618.15		$660.6272	$660.63	$660.60	$660.70