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	$142.50	5.349%	$150.1223	$150.12	$150.10	$150.10
Purchase #2	$194.35	10.745%	$215.2329	$215.23	$215.25	$215.20
Purchase #3	$158.41	5.293%	$166.7946	$166.79	$166.80	$166.80
Purchase #4	$177.82	7.108%	$190.4594	$190.46	$190.45	$190.50
Purchase #5	$151.51	7.345%	$162.6384	$162.64	$162.65	$162.60
Purchase #6	$27.58	6.105%	$29.2638	$29.26	$29.25	$29.30
Purchase #7	$163.68	9.678%	$179.521	$179.52	$179.50	$179.50
7 purchase totals =	$1,015.85		$1,094.0324	$1,094.02	$1,094.00	$1,094.00