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	$79.42	8.106%	$85.8578	$85.86	$85.85	$85.90
Purchase #2	$76.25	3.116%	$78.626	$78.63	$78.65	$78.60
Purchase #3	$77.48	9.473%	$84.8197	$84.82	$84.80	$84.80
Purchase #4	$69.72	11.277%	$77.5823	$77.58	$77.60	$77.60
Purchase #5	$166.72	11.661%	$186.1612	$186.16	$186.15	$186.20
Purchase #6	$228.32	12.113%	$255.9764	$255.98	$256.00	$256.00
Purchase #7	$249.34	12.150%	$279.6348	$279.63	$279.65	$279.60
7 purchase totals =	$947.25		$1,048.6582	$1,048.66	$1,048.70	$1,048.70