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	$41.91	6.608%	$44.6794	$44.68	$44.70	$44.70
Purchase #2	$244.65	4.296%	$255.1602	$255.16	$255.15	$255.20
Purchase #3	$56.58	7.512%	$60.8303	$60.83	$60.85	$60.80
Purchase #4	$33.46	11.705%	$37.3765	$37.38	$37.40	$37.40
Purchase #5	$10.86	9.387%	$11.8794	$11.88	$11.90	$11.90
Purchase #6	$44.76	7.735%	$48.2222	$48.22	$48.20	$48.20
Purchase #7	$97.95	4.464%	$102.3225	$102.32	$102.30	$102.30
7 purchase totals =	$530.17		$560.4705	$560.47	$560.50	$560.50