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	$11.25	11.332%	$12.5249	$12.52	$12.50	$12.50
Purchase #2	$86.33	6.491%	$91.9337	$91.93	$91.95	$91.90
Purchase #3	$51.74	13.500%	$58.7249	$58.72	$58.70	$58.70
Purchase #4	$31.43	4.218%	$32.7557	$32.76	$32.75	$32.80
Purchase #5	$134.27	8.624%	$145.8494	$145.85	$145.85	$145.80
Purchase #6	$196.25	7.413%	$210.798	$210.80	$210.80	$210.80
Purchase #7	$166.76	3.499%	$172.5949	$172.59	$172.60	$172.60
7 purchase totals =	$678.03		$725.1815	$725.17	$725.15	$725.10