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	$9.84	9.670%	$10.7915	$10.79	$10.80	$10.80
Purchase #2	$125.80	8.493%	$136.4842	$136.48	$136.50	$136.50
Purchase #3	$104.77	4.351%	$109.3285	$109.33	$109.35	$109.30
Purchase #4	$82.35	5.596%	$86.9583	$86.96	$86.95	$87.00
Purchase #5	$224.60	6.394%	$238.9609	$238.96	$238.95	$239.00
Purchase #6	$196.43	13.784%	$223.5059	$223.51	$223.50	$223.50
Purchase #7	$234.68	12.209%	$263.3321	$263.33	$263.35	$263.30
7 purchase totals =	$978.47		$1,069.3614	$1,069.36	$1,069.40	$1,069.40