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	$104.61	3.269%	$108.0297	$108.03	$108.05	$108.00
Purchase #2	$10.69	6.344%	$11.3682	$11.37	$11.35	$11.40
Purchase #3	$13.90	5.164%	$14.6178	$14.62	$14.60	$14.60
Purchase #4	$249.33	6.517%	$265.5788	$265.58	$265.60	$265.60
Purchase #5	$46.26	10.168%	$50.9637	$50.96	$50.95	$51.00
Purchase #6	$84.56	6.693%	$90.2196	$90.22	$90.20	$90.20
Purchase #7	$159.71	5.330%	$168.2225	$168.22	$168.20	$168.20
7 purchase totals =	$669.06		$709.0003	$709.00	$708.95	$709.00