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	$89.40	6.284%	$95.0179	$95.02	$95.00	$95.00
Purchase #2	$42.62	3.825%	$44.2502	$44.25	$44.25	$44.30
Purchase #3	$187.89	4.348%	$196.0595	$196.06	$196.05	$196.10
Purchase #4	$153.91	11.565%	$171.7097	$171.71	$171.70	$171.70
Purchase #5	$71.94	10.663%	$79.611	$79.61	$79.60	$79.60
Purchase #6	$8.83	12.754%	$9.9562	$9.96	$9.95	$10.00
Purchase #7	$51.51	5.371%	$54.2766	$54.28	$54.30	$54.30
7 purchase totals =	$606.10		$650.8811	$650.89	$650.85	$651.00