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	$40.96	5.419%	$43.1796	$43.18	$43.20	$43.20
Purchase #2	$227.80	12.475%	$256.2181	$256.22	$256.20	$256.20
Purchase #3	$34.37	12.375%	$38.6233	$38.62	$38.60	$38.60
Purchase #4	$213.47	4.743%	$223.5949	$223.59	$223.60	$223.60
Purchase #5	$168.81	3.261%	$174.3149	$174.31	$174.30	$174.30
Purchase #6	$210.72	12.509%	$237.079	$237.08	$237.10	$237.10
Purchase #7	$99.39	9.196%	$108.5299	$108.53	$108.55	$108.50
7 purchase totals =	$995.52		$1,081.5397	$1,081.53	$1,081.55	$1,081.50