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	$134.27	13.781%	$152.7737	$152.77	$152.75	$152.80
Purchase #2	$163.95	7.120%	$175.6232	$175.62	$175.60	$175.60
Purchase #3	$84.84	6.776%	$90.5888	$90.59	$90.60	$90.60
Purchase #4	$112.60	6.209%	$119.5913	$119.59	$119.60	$119.60
Purchase #5	$36.45	10.564%	$40.3006	$40.30	$40.30	$40.30
Purchase #6	$237.65	13.207%	$269.0364	$269.04	$269.05	$269.00
Purchase #7	$238.83	10.483%	$263.8665	$263.87	$263.85	$263.90
7 purchase totals =	$1,008.59		$1,111.7805	$1,111.78	$1,111.75	$1,111.80