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	$119.33	3.308%	$123.2774	$123.28	$123.30	$123.30
Purchase #2	$175.47	5.206%	$184.605	$184.61	$184.60	$184.60
Purchase #3	$181.97	11.748%	$203.3478	$203.35	$203.35	$203.30
Purchase #4	$241.60	10.125%	$266.062	$266.06	$266.05	$266.10
Purchase #5	$68.85	13.729%	$78.3024	$78.30	$78.30	$78.30
Purchase #6	$199.77	9.173%	$218.0949	$218.09	$218.10	$218.10
Purchase #7	$142.68	4.361%	$148.9023	$148.90	$148.90	$148.90
7 purchase totals =	$1,129.67		$1,222.5918	$1,222.59	$1,222.60	$1,222.60