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	$221.60	9.132%	$241.8365	$241.84	$241.85	$241.80
Purchase #2	$143.46	5.477%	$151.3173	$151.32	$151.30	$151.30
Purchase #3	$129.39	3.666%	$134.1334	$134.13	$134.15	$134.10
Purchase #4	$94.52	11.208%	$105.1138	$105.11	$105.10	$105.10
Purchase #5	$173.98	7.177%	$186.4665	$186.47	$186.45	$186.50
Purchase #6	$152.35	10.440%	$168.2553	$168.26	$168.25	$168.30
Purchase #7	$167.86	13.437%	$190.4153	$190.42	$190.40	$190.40
7 purchase totals =	$1,083.16		$1,177.5381	$1,177.55	$1,177.50	$1,177.50