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	$95.43	9.298%	$104.3031	$104.30	$104.30	$104.30
Purchase #2	$112.79	13.264%	$127.7505	$127.75	$127.75	$127.80
Purchase #3	$39.34	11.201%	$43.7465	$43.75	$43.75	$43.70
Purchase #4	$91.89	4.454%	$95.9828	$95.98	$96.00	$96.00
Purchase #5	$35.43	12.542%	$39.8736	$39.87	$39.85	$39.90
Purchase #6	$173.89	8.593%	$188.8324	$188.83	$188.85	$188.80
Purchase #7	$154.63	6.786%	$165.1232	$165.12	$165.10	$165.10
7 purchase totals =	$703.40		$765.6121	$765.60	$765.60	$765.60