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	$198.55	13.647%	$225.6461	$225.65	$225.65	$225.60
Purchase #2	$187.58	5.588%	$198.062	$198.06	$198.05	$198.10
Purchase #3	$74.51	11.829%	$83.3238	$83.32	$83.30	$83.30
Purchase #4	$116.31	10.188%	$128.1597	$128.16	$128.15	$128.20
Purchase #5	$129.94	7.646%	$139.8752	$139.88	$139.90	$139.90
Purchase #6	$84.99	11.713%	$94.9449	$94.94	$94.95	$94.90
Purchase #7	$83.37	7.449%	$89.5802	$89.58	$89.60	$89.60
7 purchase totals =	$875.25		$959.5919	$959.59	$959.60	$959.60