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	$105.43	5.416%	$111.1401	$111.14	$111.15	$111.10
Purchase #2	$141.26	8.256%	$152.9224	$152.92	$152.90	$152.90
Purchase #3	$156.31	7.349%	$167.7972	$167.80	$167.80	$167.80
Purchase #4	$93.88	6.628%	$100.1024	$100.10	$100.10	$100.10
Purchase #5	$206.94	9.413%	$226.4193	$226.42	$226.40	$226.40
Purchase #6	$20.42	5.170%	$21.4757	$21.48	$21.50	$21.50
Purchase #7	$63.38	8.202%	$68.5784	$68.58	$68.60	$68.60
7 purchase totals =	$787.62		$848.4355	$848.44	$848.45	$848.40