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	$210.56	9.866%	$231.3338	$231.33	$231.35	$231.30
Purchase #2	$149.83	6.657%	$159.8042	$159.80	$159.80	$159.80
Purchase #3	$114.57	3.548%	$118.6349	$118.63	$118.65	$118.60
Purchase #4	$191.83	8.690%	$208.5	$208.50	$208.50	$208.50
Purchase #5	$172.56	10.253%	$190.2526	$190.25	$190.25	$190.30
Purchase #6	$107.86	7.518%	$115.9689	$115.97	$115.95	$116.00
Purchase #7	$152.32	12.645%	$171.5809	$171.58	$171.60	$171.60
7 purchase totals =	$1,099.53		$1,196.0753	$1,196.06	$1,196.10	$1,196.10