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	$144.67	5.698%	$152.9133	$152.91	$152.90	$152.90
Purchase #2	$119.55	8.359%	$129.5432	$129.54	$129.55	$129.50
Purchase #3	$90.87	9.402%	$99.4136	$99.41	$99.40	$99.40
Purchase #4	$6.40	8.491%	$6.9434	$6.94	$6.95	$6.90
Purchase #5	$171.73	3.239%	$177.2923	$177.29	$177.30	$177.30
Purchase #6	$148.28	3.138%	$152.933	$152.93	$152.95	$152.90
Purchase #7	$196.46	6.699%	$209.6209	$209.62	$209.60	$209.60
7 purchase totals =	$877.96		$928.6597	$928.64	$928.65	$928.50