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	$33.43	11.661%	$37.3283	$37.33	$37.35	$37.30
Purchase #2	$140.62	7.217%	$150.7685	$150.77	$150.75	$150.80
Purchase #3	$5.81	13.595%	$6.5999	$6.60	$6.60	$6.60
Purchase #4	$110.71	5.129%	$116.3883	$116.39	$116.40	$116.40
Purchase #5	$93.44	13.138%	$105.7161	$105.72	$105.70	$105.70
Purchase #6	$239.58	13.778%	$272.5893	$272.59	$272.60	$272.60
Purchase #7	$38.50	5.534%	$40.6306	$40.63	$40.65	$40.60
7 purchase totals =	$662.09		$730.0210	$730.03	$730.05	$730.00