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	$49.80	4.778%	$52.1794	$52.18	$52.20	$52.20
Purchase #2	$118.32	7.455%	$127.1408	$127.14	$127.15	$127.10
Purchase #3	$63.93	12.364%	$71.8343	$71.83	$71.85	$71.80
Purchase #4	$97.60	6.781%	$104.2183	$104.22	$104.20	$104.20
Purchase #5	$212.36	8.610%	$230.6442	$230.64	$230.65	$230.60
Purchase #6	$19.91	5.838%	$21.0723	$21.07	$21.05	$21.10
Purchase #7	$94.77	5.693%	$100.1653	$100.17	$100.15	$100.20
7 purchase totals =	$656.69		$707.2546	$707.25	$707.25	$707.20