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	$228.66	4.513%	$238.9794	$238.98	$239.00	$239.00
Purchase #2	$88.74	12.770%	$100.0721	$100.07	$100.05	$100.10
Purchase #3	$75.92	12.123%	$85.1238	$85.12	$85.10	$85.10
Purchase #4	$242.41	13.461%	$275.0408	$275.04	$275.05	$275.00
Purchase #5	$112.85	9.242%	$123.2796	$123.28	$123.30	$123.30
Purchase #6	$224.77	10.462%	$248.2854	$248.29	$248.30	$248.30
Purchase #7	$138.40	5.475%	$145.9774	$145.98	$146.00	$146.00
7 purchase totals =	$1,111.75		$1,216.7585	$1,216.76	$1,216.80	$1,216.80