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	$54.33	8.600%	$59.0024	$59.00	$59.00	$59.00
Purchase #2	$34.38	4.153%	$35.8078	$35.81	$35.80	$35.80
Purchase #3	$152.27	4.730%	$159.4724	$159.47	$159.45	$159.50
Purchase #4	$9.57	6.468%	$10.189	$10.19	$10.20	$10.20
Purchase #5	$146.48	4.671%	$153.3221	$153.32	$153.30	$153.30
Purchase #6	$136.72	10.204%	$150.6709	$150.67	$150.65	$150.70
Purchase #7	$52.75	7.420%	$56.6641	$56.66	$56.65	$56.70
7 purchase totals =	$586.50		$625.1287	$625.12	$625.05	$625.20