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	$76.59	12.116%	$85.8696	$85.87	$85.85	$85.90
Purchase #2	$241.80	13.576%	$274.6268	$274.63	$274.65	$274.60
Purchase #3	$84.34	10.114%	$92.8701	$92.87	$92.85	$92.90
Purchase #4	$223.25	4.493%	$233.2806	$233.28	$233.30	$233.30
Purchase #5	$128.80	10.850%	$142.7748	$142.77	$142.75	$142.80
Purchase #6	$50.39	7.193%	$54.0146	$54.01	$54.00	$54.00
Purchase #7	$54.80	5.466%	$57.7954	$57.80	$57.80	$57.80
7 purchase totals =	$859.97		$941.2319	$941.23	$941.20	$941.30