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	$163.88	13.269%	$185.6252	$185.63	$185.65	$185.60
Purchase #2	$105.98	11.575%	$118.2472	$118.25	$118.25	$118.20
Purchase #3	$17.52	6.138%	$18.5954	$18.60	$18.60	$18.60
Purchase #4	$179.87	4.847%	$188.5883	$188.59	$188.60	$188.60
Purchase #5	$144.27	6.272%	$153.3186	$153.32	$153.30	$153.30
Purchase #6	$39.26	11.663%	$43.8389	$43.84	$43.85	$43.80
Purchase #7	$15.92	13.280%	$18.0342	$18.03	$18.05	$18.00
7 purchase totals =	$666.70		$726.2478	$726.26	$726.30	$726.10