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	$86.45	7.418%	$92.8629	$92.86	$92.85	$92.90
Purchase #2	$170.96	12.776%	$192.8018	$192.80	$192.80	$192.80
Purchase #3	$75.39	9.771%	$82.7564	$82.76	$82.75	$82.80
Purchase #4	$79.57	7.440%	$85.49	$85.49	$85.50	$85.50
Purchase #5	$9.94	6.319%	$10.5681	$10.57	$10.55	$10.60
Purchase #6	$96.44	4.528%	$100.8068	$100.81	$100.80	$100.80
Purchase #7	$127.39	12.321%	$143.0857	$143.09	$143.10	$143.10
7 purchase totals =	$646.14		$708.3717	$708.38	$708.35	$708.50