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	$50.75	7.622%	$54.6182	$54.62	$54.60	$54.60
Purchase #2	$80.52	6.357%	$85.6387	$85.64	$85.65	$85.60
Purchase #3	$15.62	3.357%	$16.1444	$16.14	$16.15	$16.10
Purchase #4	$123.76	12.381%	$139.0827	$139.08	$139.10	$139.10
Purchase #5	$87.28	13.535%	$99.0933	$99.09	$99.10	$99.10
Purchase #6	$32.68	7.636%	$35.1754	$35.18	$35.20	$35.20
Purchase #7	$227.92	6.822%	$243.4687	$243.47	$243.45	$243.50
7 purchase totals =	$618.53		$673.2214	$673.22	$673.25	$673.20