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	$179.71	9.530%	$196.8364	$196.84	$196.85	$196.80
Purchase #2	$166.36	3.697%	$172.5103	$172.51	$172.50	$172.50
Purchase #3	$131.85	4.727%	$138.0825	$138.08	$138.10	$138.10
Purchase #4	$206.43	8.491%	$223.958	$223.96	$223.95	$224.00
Purchase #5	$62.63	12.593%	$70.517	$70.52	$70.50	$70.50
Purchase #6	$206.70	5.750%	$218.5853	$218.59	$218.60	$218.60
Purchase #7	$76.79	10.345%	$84.7339	$84.73	$84.75	$84.70
7 purchase totals =	$1,030.47		$1,105.2234	$1,105.23	$1,105.25	$1,105.20