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	$168.52	12.635%	$189.8125	$189.81	$189.80	$189.80
Purchase #2	$87.59	12.534%	$98.5685	$98.57	$98.55	$98.60
Purchase #3	$105.49	5.283%	$111.063	$111.06	$111.05	$111.10
Purchase #4	$19.56	10.353%	$21.585	$21.59	$21.60	$21.60
Purchase #5	$199.48	12.630%	$224.6743	$224.67	$224.65	$224.70
Purchase #6	$89.97	4.606%	$94.114	$94.11	$94.10	$94.10
Purchase #7	$74.47	4.224%	$77.6156	$77.62	$77.60	$77.60
7 purchase totals =	$745.08		$817.4329	$817.43	$817.35	$817.50