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	$203.30	11.742%	$227.1715	$227.17	$227.15	$227.20
Purchase #2	$90.34	5.714%	$95.502	$95.50	$95.50	$95.50
Purchase #3	$92.31	4.422%	$96.3919	$96.39	$96.40	$96.40
Purchase #4	$151.42	10.379%	$167.1359	$167.14	$167.15	$167.10
Purchase #5	$164.92	4.584%	$172.4799	$172.48	$172.50	$172.50
Purchase #6	$113.55	12.248%	$127.4576	$127.46	$127.45	$127.50
Purchase #7	$24.59	12.245%	$27.601	$27.60	$27.60	$27.60
7 purchase totals =	$840.43		$913.7398	$913.74	$913.75	$913.80