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	$41.89	3.143%	$43.2066	$43.21	$43.20	$43.20
Purchase #2	$12.52	12.647%	$14.1034	$14.10	$14.10	$14.10
Purchase #3	$116.78	9.466%	$127.8344	$127.83	$127.85	$127.80
Purchase #4	$73.95	5.730%	$78.1873	$78.19	$78.20	$78.20
Purchase #5	$76.86	12.724%	$86.6397	$86.64	$86.65	$86.60
Purchase #6	$75.52	8.566%	$81.989	$81.99	$82.00	$82.00
Purchase #7	$179.76	11.559%	$200.5385	$200.54	$200.55	$200.50
7 purchase totals =	$577.28		$632.4989	$632.50	$632.55	$632.40