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	$231.59	5.575%	$244.5011	$244.50	$244.50	$244.50
Purchase #2	$216.67	4.870%	$227.2218	$227.22	$227.20	$227.20
Purchase #3	$112.75	3.440%	$116.6286	$116.63	$116.65	$116.60
Purchase #4	$40.56	6.769%	$43.3055	$43.31	$43.30	$43.30
Purchase #5	$15.51	12.687%	$17.4778	$17.48	$17.50	$17.50
Purchase #6	$105.50	12.414%	$118.5968	$118.60	$118.60	$118.60
Purchase #7	$115.26	11.468%	$128.478	$128.48	$128.50	$128.50
7 purchase totals =	$837.84		$896.2096	$896.22	$896.25	$896.20