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	$53.64	11.598%	$59.8612	$59.86	$59.85	$59.90
Purchase #2	$167.58	6.749%	$178.89	$178.89	$178.90	$178.90
Purchase #3	$60.93	6.834%	$65.094	$65.09	$65.10	$65.10
Purchase #4	$216.34	3.782%	$224.522	$224.52	$224.50	$224.50
Purchase #5	$105.98	5.672%	$111.9912	$111.99	$112.00	$112.00
Purchase #6	$151.84	11.160%	$168.7853	$168.79	$168.80	$168.80
Purchase #7	$15.68	4.345%	$16.3613	$16.36	$16.35	$16.40
7 purchase totals =	$771.99		$825.5050	$825.50	$825.50	$825.60