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	$10.25	3.554%	$10.6143	$10.61	$10.60	$10.60
Purchase #2	$100.39	3.629%	$104.0332	$104.03	$104.05	$104.00
Purchase #3	$150.66	5.473%	$158.9056	$158.91	$158.90	$158.90
Purchase #4	$123.75	6.785%	$132.1464	$132.15	$132.15	$132.10
Purchase #5	$92.36	11.751%	$103.2132	$103.21	$103.20	$103.20
Purchase #6	$33.62	3.488%	$34.7927	$34.79	$34.80	$34.80
Purchase #7	$135.43	6.564%	$144.3196	$144.32	$144.30	$144.30
7 purchase totals =	$646.46		$688.0250	$688.02	$688.00	$687.90