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	$231.89	10.456%	$256.1364	$256.14	$256.15	$256.10
Purchase #2	$26.79	5.578%	$28.2843	$28.28	$28.30	$28.30
Purchase #3	$42.99	5.612%	$45.4026	$45.40	$45.40	$45.40
Purchase #4	$136.85	6.663%	$145.9683	$145.97	$145.95	$146.00
Purchase #5	$105.70	10.127%	$116.4042	$116.40	$116.40	$116.40
Purchase #6	$17.50	3.744%	$18.1552	$18.16	$18.15	$18.20
Purchase #7	$96.50	7.596%	$103.8301	$103.83	$103.85	$103.80
7 purchase totals =	$658.22		$714.1811	$714.18	$714.20	$714.20